feat: dark mode background fixes, chat bubble long-press menu, notification dedup, biometric auth for clear

- Fix: dark mode white backgrounds via transparent windowBackground, decorView color, and explicit Surface backgrounds on IoT/Profile/MainScreen
- Fix: dark mode text colors in ProfileScreen (nickname, account info, assistant status)
- Feat: long-press chat bubble to copy message text via DropdownMenu
- Feat: notification deduplication — track notified message IDs, clear on foreground
- Feat: cancel all notifications when app enters foreground
- Feat: biometric/device-credential verification before clearing local messages

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

gradle/libs.versions.toml

@@ -56,6 +56,9 @@ coroutines = { group = "org.jetbrains.kotlinx", name = "kotlinx-coroutines-andro
 # Core
 core-ktx = { group = "androidx.core", name = "core-ktx", version = "1.15.0" }
 
+# Biometric
+biometric = { group = "androidx.biometric", name = "biometric", version = "1.1.0" }
+
 [plugins]
 android-application = { id = "com.android.application", version.ref = "agp" }
 kotlin-android = { id = "org.jetbrains.kotlin.android", version.ref = "kotlin" }