Native Google Play Services Sign-In, Handle-First Bluesky OAuth 2.1 & Full 12-Theme Palette Parity for Android

• 🔐 Native In-App Google Sign-In: Integrated Google Play Services Auth (play-services-auth:21.3.0) with GoogleSignInClient, launching the native Android OS-level account picker bottom sheet directly within the app with zero browser redirects.
• 🦋 Handle-First Bluesky OAuth 2.1 (Zero App Passwords): Retired manual app password fields on Android in favor of decentralized AT Protocol OAuth 2.1 + DPoP, featuring automatic PDS resolution and instant deep link handoff (webnerdai://auth/callback).
• 🎨 Full 12-Theme Palette Parity: Ported all 8 desktop retro and pastel palettes (Mac OS 9 Classic, Mac OS X Aqua, BeOS R5, Retro Android Cupcake, Lavender, Mint, Peach, Sky, Rose) to Compose ColorScheme with horizontally scrollable selector chips.
• 🛠️ Dual Google Client ID Verification: Enhanced backend verification to seamlessly accept both Web and Android OAuth 2.0 client IDs across audience and authorized party (azp) claims.