Fix white content on amber surfaces in dark theme

The dark palette left onPrimary/onPrimaryContainer/onSecondaryContainer
at the darkColorScheme defaults (white) while mapping amber into the
matching container roles, so dark theme rendered white text and icons
on light-amber surfaces: the Edit Relays floating action button, the
add-relay icon buttons, selected filter chips on the feedback screen,
and other primary-container components.

Set the on-colors to black in both palettes (amber is light in both),
give the add-relay IconButtons an explicit theme-driven contentColor
instead of the onSurface fallback, and drop the redundant hardcoded
black icon tints.

app/src/main/java/com/greenart7c3/nostrsigner/ui/AuthWhitelistScreen.kt

@@ -133,6 +133,7 @@ fun AuthWhitelistScreen(
                     IconButton(
                         colors = IconButtonDefaults.iconButtonColors().copy(
                             containerColor = MaterialTheme.colorScheme.primary,
+                            contentColor = MaterialTheme.colorScheme.onPrimary,
                         ),
                         onClick = { addEntry() },
                     ) {

app/src/main/java/com/greenart7c3/nostrsigner/ui/DefaultProfileRelaysScreen.kt

@@ -195,6 +195,7 @@ fun DefaultProfileRelaysScreen(
                         IconButton(
                             colors = IconButtonDefaults.iconButtonColors().copy(
                                 containerColor = MaterialTheme.colorScheme.primary,
+                                contentColor = MaterialTheme.colorScheme.onPrimary,
                             ),
                             onClick = {
                                 scope.launch(Dispatchers.IO) {

app/src/main/java/com/greenart7c3/nostrsigner/ui/EditConfigurationScreen.kt

@@ -206,6 +206,7 @@ fun EditConfigurationScreen(
                         IconButton(
                             colors = IconButtonDefaults.iconButtonColors().copy(
                                 containerColor = MaterialTheme.colorScheme.primary,
+                                contentColor = MaterialTheme.colorScheme.onPrimary,
                             ),
                             onClick = {
                                 scope.launch(Dispatchers.IO) {

app/src/main/java/com/greenart7c3/nostrsigner/ui/NewNsecBunkerScreen.kt

@@ -35,7 +35,6 @@ import androidx.compose.ui.Modifier
 import androidx.compose.ui.focus.FocusDirection
 import androidx.compose.ui.focus.FocusRequester
 import androidx.compose.ui.focus.focusRequester
-import androidx.compose.ui.graphics.Color
 import androidx.compose.ui.platform.ClipEntry
 import androidx.compose.ui.platform.LocalClipboard
 import androidx.compose.ui.platform.LocalContext
@@ -197,6 +196,7 @@ fun NewNsecBunkerScreen(
                         IconButton(
                             colors = IconButtonDefaults.iconButtonColors().copy(
                                 containerColor = MaterialTheme.colorScheme.primary,
+                                contentColor = MaterialTheme.colorScheme.onPrimary,
                             ),
                             onClick = {
                                 scope.launch(Dispatchers.IO) {
@@ -216,7 +216,6 @@ fun NewNsecBunkerScreen(
                             Icon(
                                 Icons.Default.Add,
                                 null,
-                                tint = Color.Black,
                             )
                         }
                     },

app/src/main/java/com/greenart7c3/nostrsigner/ui/actions/EditRelaysDialog.kt

@@ -241,6 +241,7 @@ fun DefaultRelaysScreen(
                         IconButton(
                             colors = IconButtonDefaults.iconButtonColors().copy(
                                 containerColor = MaterialTheme.colorScheme.primary,
+                                contentColor = MaterialTheme.colorScheme.onPrimary,
                             ),
                             onClick = {
                                 scope.launch(Dispatchers.IO) {

app/src/main/java/com/greenart7c3/nostrsigner/ui/components/AmberFloatingButton.kt

@@ -10,7 +10,6 @@ import androidx.compose.material3.Text
 import androidx.compose.runtime.Composable
 import androidx.compose.ui.Alignment
 import androidx.compose.ui.Modifier
-import androidx.compose.ui.graphics.Color
 import androidx.compose.ui.graphics.vector.ImageVector
 import androidx.compose.ui.res.stringResource
 import androidx.compose.ui.res.vectorResource
@@ -44,7 +43,6 @@ fun AmberFloatingButton(
                     Icon(
                         ImageVector.vectorResource(R.drawable.settings),
                         contentDescription = stringResource(R.string.edit_relays),
-                        tint = Color.Black,
                     )
                 },
                 modifier = Modifier

app/src/main/java/com/greenart7c3/nostrsigner/ui/components/NewBunkerFloatingButton.kt

@@ -11,7 +11,6 @@ import androidx.compose.material3.Icon
 import androidx.compose.runtime.Composable
 import androidx.compose.ui.Alignment
 import androidx.compose.ui.Modifier
-import androidx.compose.ui.graphics.Color
 import androidx.compose.ui.res.stringResource
 import androidx.compose.ui.unit.dp
 import com.greenart7c3.nostrsigner.R
@@ -40,7 +39,6 @@ fun NewBunkerFloatingButton(
             Icon(
                 Icons.Default.Add,
                 contentDescription = stringResource(R.string.connect_app),
-                tint = Color.Black,
             )
         }
     }

app/src/main/java/com/greenart7c3/nostrsigner/ui/theme/Theme.kt

@@ -41,16 +41,19 @@ val orange = Color(0xFFFF6B00)
 private val DarkColorPalette =
     darkColorScheme(
         primary = primaryColor,
-        onPrimary = Color.White,
+        onPrimary = Color.Black,
         secondary = primaryVariant,
         tertiary = secondaryColor,
         primaryContainer = secondaryColor,
+        onPrimaryContainer = Color.Black,
         secondaryContainer = secondaryColor,
+        onSecondaryContainer = Color.Black,
     )
 
 private val LightColorPalette =
     lightColorScheme(
         primary = primaryColor,
+        onPrimary = Color.Black,
         secondary = primaryVariant,
         tertiary = secondaryColor,
         primaryContainer = secondaryColor,