refactor: move ToS / legal links into flavor source sets

The Play-Store-only Terms-of-Use checkbox and the "About & Legal"
Settings section both contain hardcoded GitHub URLs to the published
PRIVACY.md. Previously they were in src/main and gated at call sites
by `BuildConfig.FLAVOR == "play"` — which works at runtime but still
compiles the GitHub URLs into the F-Droid APK.

This commit moves the URL-bearing UI into src/play and adds empty
src/fdroid stubs with the same signatures, so the F-Droid build is
physically free of the URLs.

New composables (same package + signature in both flavor source sets,
so callers in src/main link to whichever flavor is being built):

- com.vitorpamplona.amethyst.ui.screen.loggedOff.legal.TermsGate
  * src/play: renders an AcceptTerms checkbox with the PRIVACY.md link
    and the "acceptance required" error text.
  * src/fdroid: empty body.

- com.vitorpamplona.amethyst.ui.screen.loggedIn.settings.LegalSettingsSection
  * src/play: renders the SettingsSection with Privacy Policy and
    Child Safety Standards rows that open the GitHub-hosted PRIVACY.md.
  * src/fdroid: empty body.

Call-site changes:

- LoginScreen: drop `BuildConfig.FLAVOR == "play"` guard and call
  `TermsGate(...)` inside the existing `isFirstLogin` block. The
  flavor source set picks the right body.
- SignUpScreen: drop `BuildConfig.FLAVOR == "play"` guard, call
  `TermsGate(...)` unconditionally.
- AllSettingsScreen: drop `BuildConfig.FLAVOR == "play"` guard and
  the inline About & Legal SettingsSection, call
  `LegalSettingsSection()` instead. LocalUriHandler and BuildConfig
  imports removed.

The old `src/main/.../loggedOff/AcceptTerms.kt` is deleted; its body
moves into the play-flavor TermsGate as a file-private helper.

The LoginViewModel / SignUpViewModel still use `BuildConfig.FLAVOR` to
decide the initial `acceptedTerms` value (so the login/signup button
isn't disabled on F-Droid). That check is logic only, contains no
URLs, and is safe for F-Droid distribution.

Verified: `grep -r "github.com/vitorpamplona/amethyst/blob"` against
src/main + src/fdroid returns zero matches. Both
:amethyst:compileFdroidDebugKotlin and :amethyst:compilePlayDebugKotlin
compile cleanly.

amethyst/src/fdroid/java/com/vitorpamplona/amethyst/ui/screen/loggedIn/settings/LegalSettingsSection.kt

@@ -0,0 +1,29 @@
+/*
+ * Copyright (c) 2025 Vitor Pamplona
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy of
+ * this software and associated documentation files (the "Software"), to deal in
+ * the Software without restriction, including without limitation the rights to use,
+ * copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the
+ * Software, and to permit persons to whom the Software is furnished to do so,
+ * subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in all
+ * copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS
+ * FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR
+ * COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN
+ * AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION
+ * WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
+ */
+package com.vitorpamplona.amethyst.ui.screen.loggedIn.settings
+
+import androidx.compose.runtime.Composable
+
+// F-Droid distributes Amethyst as MIT-licensed free software; the build must
+// not surface links to external (e.g. GitHub-hosted) policy documents.
+@Composable
+fun LegalSettingsSection() {
+}

amethyst/src/fdroid/java/com/vitorpamplona/amethyst/ui/screen/loggedOff/legal/TermsGate.kt

@@ -0,0 +1,35 @@
+/*
+ * Copyright (c) 2025 Vitor Pamplona
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy of
+ * this software and associated documentation files (the "Software"), to deal in
+ * the Software without restriction, including without limitation the rights to use,
+ * copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the
+ * Software, and to permit persons to whom the Software is furnished to do so,
+ * subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in all
+ * copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS
+ * FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR
+ * COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN
+ * AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION
+ * WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
+ */
+package com.vitorpamplona.amethyst.ui.screen.loggedOff.legal
+
+import androidx.compose.runtime.Composable
+
+// F-Droid distributes Amethyst as MIT-licensed free software; there is no
+// terms-of-use acceptance layered on top of the source license, and the build
+// must not link to any external (e.g. GitHub) policy document.
+@Composable
+@Suppress("UNUSED_PARAMETER")
+fun TermsGate(
+    checked: Boolean,
+    onCheckedChange: (Boolean) -> Unit,
+    showError: Boolean,
+) {
+}

amethyst/src/main/java/com/vitorpamplona/amethyst/ui/screen/loggedIn/settings/AllSettingsScreen.kt

@@ -42,11 +42,9 @@ import androidx.compose.runtime.rememberCoroutineScope
 import androidx.compose.runtime.setValue
 import androidx.compose.ui.Modifier
 import androidx.compose.ui.platform.LocalContext
-import androidx.compose.ui.platform.LocalUriHandler
 import androidx.compose.ui.text.style.TextAlign
 import androidx.compose.ui.tooling.preview.Preview
 import androidx.compose.ui.unit.dp
-import com.vitorpamplona.amethyst.BuildConfig
 import com.vitorpamplona.amethyst.R
 import com.vitorpamplona.amethyst.commons.icons.symbols.Icon
 import com.vitorpamplona.amethyst.commons.icons.symbols.MaterialSymbols
@@ -79,7 +77,6 @@ fun AllSettingsScreen(
     nav: INav,
 ) {
     val context = LocalContext.current
-    val uriHandler = LocalUriHandler.current
     val scope = rememberCoroutineScope()
     var showResetMarmotDialog by remember { mutableStateOf(false) }
     var isResettingMarmot by remember { mutableStateOf(false) }
@@ -264,33 +261,7 @@ fun AllSettingsScreen(
                 )
             }
 
-            if (BuildConfig.FLAVOR == "play") {
-                SettingsSection(R.string.about_legal) {
-                    SettingsItem(
-                        title = R.string.privacy_policy,
-                        icon = MaterialSymbols.Lock,
-                        onClick = {
-                            runCatching {
-                                uriHandler.openUri(
-                                    "https://github.com/vitorpamplona/amethyst/blob/main/PRIVACY.md",
-                                )
-                            }
-                        },
-                    )
-                    SettingsDivider()
-                    SettingsItem(
-                        title = R.string.child_safety_standards,
-                        icon = MaterialSymbols.Shield,
-                        onClick = {
-                            runCatching {
-                                uriHandler.openUri(
-                                    "https://github.com/vitorpamplona/amethyst/blob/main/PRIVACY.md#child-safety-standards",
-                                )
-                            }
-                        },
-                    )
-                }
-            }
+            LegalSettingsSection()
 
             SettingsSection(R.string.danger_zone, isDanger = true) {
                 if (hasPrivateKey) {

amethyst/src/main/java/com/vitorpamplona/amethyst/ui/screen/loggedOff/login/LoginScreen.kt

@@ -66,15 +66,14 @@ import androidx.compose.ui.tooling.preview.Preview
 import androidx.compose.ui.unit.dp
 import androidx.lifecycle.viewmodel.compose.viewModel
 import com.vitorpamplona.amethyst.Amethyst
-import com.vitorpamplona.amethyst.BuildConfig
 import com.vitorpamplona.amethyst.R
 import com.vitorpamplona.amethyst.commons.hashtags.Amethyst
 import com.vitorpamplona.amethyst.commons.hashtags.CustomHashTagIcons
 import com.vitorpamplona.amethyst.commons.icons.symbols.Icon
 import com.vitorpamplona.amethyst.commons.icons.symbols.MaterialSymbols
 import com.vitorpamplona.amethyst.ui.screen.AccountSessionManager
-import com.vitorpamplona.amethyst.ui.screen.loggedOff.AcceptTerms
 import com.vitorpamplona.amethyst.ui.screen.loggedOff.TorSettingsSetup
+import com.vitorpamplona.amethyst.ui.screen.loggedOff.legal.TermsGate
 import com.vitorpamplona.amethyst.ui.stringRes
 import com.vitorpamplona.amethyst.ui.theme.Size10dp
 import com.vitorpamplona.amethyst.ui.theme.Size20dp
@@ -197,19 +196,12 @@ fun LoginPage(
             )
         }
 
-        if (loginViewModel.isFirstLogin && BuildConfig.FLAVOR == "play") {
-            AcceptTerms(
+        if (loginViewModel.isFirstLogin) {
+            TermsGate(
                 checked = loginViewModel.acceptedTerms,
                 onCheckedChange = loginViewModel::updateAcceptedTerms,
+                showError = loginViewModel.termsAcceptanceIsRequiredError,
             )
-
-            if (loginViewModel.termsAcceptanceIsRequiredError) {
-                Text(
-                    text = stringRes(R.string.acceptance_of_terms_is_required),
-                    color = MaterialTheme.colorScheme.error,
-                    style = MaterialTheme.typography.bodySmall,
-                )
-            }
         }
 
         Spacer(modifier = Modifier.height(Size10dp))

amethyst/src/main/java/com/vitorpamplona/amethyst/ui/screen/loggedOff/signup/SignUpScreen.kt

@@ -50,13 +50,12 @@ import androidx.compose.ui.tooling.preview.Preview
 import androidx.compose.ui.unit.dp
 import androidx.lifecycle.viewmodel.compose.viewModel
 import com.vitorpamplona.amethyst.Amethyst
-import com.vitorpamplona.amethyst.BuildConfig
 import com.vitorpamplona.amethyst.R
 import com.vitorpamplona.amethyst.commons.hashtags.Amethyst
 import com.vitorpamplona.amethyst.commons.hashtags.CustomHashTagIcons
 import com.vitorpamplona.amethyst.ui.screen.AccountSessionManager
-import com.vitorpamplona.amethyst.ui.screen.loggedOff.AcceptTerms
 import com.vitorpamplona.amethyst.ui.screen.loggedOff.TorSettingsSetup
+import com.vitorpamplona.amethyst.ui.screen.loggedOff.legal.TermsGate
 import com.vitorpamplona.amethyst.ui.screen.loggedOff.login.LoginErrorManager
 import com.vitorpamplona.amethyst.ui.stringRes
 import com.vitorpamplona.amethyst.ui.theme.Size10dp
@@ -188,20 +187,11 @@ fun SignUpPage(
             },
         )
 
-        if (BuildConfig.FLAVOR == "play") {
-            AcceptTerms(
-                checked = signUpViewModel.acceptedTerms,
-                onCheckedChange = signUpViewModel::updateAcceptedTerms,
-            )
-
-            if (signUpViewModel.termsAcceptanceIsRequiredError) {
-                Text(
-                    text = stringRes(R.string.acceptance_of_terms_is_required),
-                    color = MaterialTheme.colorScheme.error,
-                    style = MaterialTheme.typography.bodySmall,
-                )
-            }
-        }
+        TermsGate(
+            checked = signUpViewModel.acceptedTerms,
+            onCheckedChange = signUpViewModel::updateAcceptedTerms,
+            showError = signUpViewModel.termsAcceptanceIsRequiredError,
+        )
 
         Spacer(modifier = Modifier.height(Size10dp))
 

amethyst/src/play/java/com/vitorpamplona/amethyst/ui/screen/loggedIn/settings/LegalSettingsSection.kt

@@ -0,0 +1,57 @@
+/*
+ * Copyright (c) 2025 Vitor Pamplona
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy of
+ * this software and associated documentation files (the "Software"), to deal in
+ * the Software without restriction, including without limitation the rights to use,
+ * copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the
+ * Software, and to permit persons to whom the Software is furnished to do so,
+ * subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in all
+ * copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS
+ * FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR
+ * COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN
+ * AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION
+ * WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
+ */
+package com.vitorpamplona.amethyst.ui.screen.loggedIn.settings
+
+import androidx.compose.runtime.Composable
+import androidx.compose.ui.platform.LocalUriHandler
+import com.vitorpamplona.amethyst.R
+import com.vitorpamplona.amethyst.commons.icons.symbols.MaterialSymbols
+
+@Composable
+fun LegalSettingsSection() {
+    val uriHandler = LocalUriHandler.current
+
+    SettingsSection(R.string.about_legal) {
+        SettingsItem(
+            title = R.string.privacy_policy,
+            icon = MaterialSymbols.Lock,
+            onClick = {
+                runCatching {
+                    uriHandler.openUri(
+                        "https://github.com/vitorpamplona/amethyst/blob/main/PRIVACY.md",
+                    )
+                }
+            },
+        )
+        SettingsDivider()
+        SettingsItem(
+            title = R.string.child_safety_standards,
+            icon = MaterialSymbols.Shield,
+            onClick = {
+                runCatching {
+                    uriHandler.openUri(
+                        "https://github.com/vitorpamplona/amethyst/blob/main/PRIVACY.md#child-safety-standards",
+                    )
+                }
+            },
+        )
+    }
+}

amethyst/src/play/java/com/vitorpamplona/amethyst/ui/screen/loggedOff/legal/TermsGate.kt

@@ -18,7 +18,7 @@
  * AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION
  * WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
  */
-package com.vitorpamplona.amethyst.ui.screen.loggedOff
+package com.vitorpamplona.amethyst.ui.screen.loggedOff.legal
 
 import androidx.compose.foundation.layout.Row
 import androidx.compose.material3.Checkbox
@@ -33,9 +33,26 @@ import com.vitorpamplona.amethyst.ui.components.appendLink
 import com.vitorpamplona.amethyst.ui.stringRes
 
 @Composable
-fun AcceptTerms(
+fun TermsGate(
     checked: Boolean,
-    onCheckedChange: ((Boolean) -> Unit)?,
+    onCheckedChange: (Boolean) -> Unit,
+    showError: Boolean,
+) {
+    AcceptTerms(checked = checked, onCheckedChange = onCheckedChange)
+
+    if (showError) {
+        Text(
+            text = stringRes(R.string.acceptance_of_terms_is_required),
+            color = MaterialTheme.colorScheme.error,
+            style = MaterialTheme.typography.bodySmall,
+        )
+    }
+}
+
+@Composable
+private fun AcceptTerms(
+    checked: Boolean,
+    onCheckedChange: (Boolean) -> Unit,
 ) {
     Row(verticalAlignment = Alignment.CenterVertically) {
         Checkbox(