fix: clear compiler warnings across all modules

Sweep of Kotlin compiler warnings in every module's main source sets
(quartz, commons, cli, desktopApp, amethyst, nappletHost).

Genuine code fixes:
- Drop unnecessary !!/safe-calls and redundant elvis/casts (OkHttp's
  now-non-null `body`, smart-cast callbacks, non-null String receivers).
- Remove provably-redundant conditions (`canvas == null` after a
  non-null content check; `account != null` implied by `canModerate`).
- Migrate deprecated kotlinx.collections.immutable persistent ops
  (add/remove/put/addAll -> adding/removing/putting/addingAll).
- Migrate LocalClipboardManager -> LocalClipboard (+ scoped setText),
  ContextCompat.startActivity -> context.startActivity, TabRow ->
  SecondaryTabRow, and @ConsistentCopyVisibility on a private-ctor data class.
- Delete dead ReceiveDialog.onGenerate param (never invoked).
- Fix a platform-Boolean type-mismatch on a ThreadLocal read.

Deprecations with no available successor are narrowly @Suppress-ed with
a reason: androidx.security.crypto (EncryptedSharedPreferences/MasterKey),
androidx.privacysandbox.ui, WebView.databaseEnabled, BluetoothDevice
.connectGatt, media3 setEnableAudioTrackPlaybackParams, FirebaseMessaging
.token, and InputMethodManager.SHOW_IMPLICIT.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_015Xb9YbBqhdZsHxMzitmyvn

commons/src/androidMain/kotlin/com/vitorpamplona/amethyst/commons/keystorage/SecureKeyStorage.kt

@@ -64,6 +64,9 @@ actual class SecureKeyStorage private actual constructor() {
         }
     }
 
+    // androidx.security.crypto is deprecated with no drop-in successor; migrating the
+    // on-disk key store is a separate, security-sensitive effort.
+    @Suppress("DEPRECATION")
     private val masterKey: MasterKey by lazy {
         MasterKey
             .Builder(appContext, MasterKey.DEFAULT_MASTER_KEY_ALIAS)
@@ -71,6 +74,7 @@ actual class SecureKeyStorage private actual constructor() {
             .build()
     }
 
+    @Suppress("DEPRECATION")
     private val encryptedPrefs by lazy {
         EncryptedSharedPreferences.create(
             appContext,