feat(discord): integrate Discord Social SDK and native Rich Presence

[Himanth-reddy]

Summary

Integrates the Discord Social SDK and native C++ JNI bridge into ARVIO for Discord Rich Presence and OAuth2 account connection. Displays real-time watch activity, movie/show poster artwork, episode information, and elapsed playback position on users' Discord profiles.

Key Changes

• Native C++ JNI Bridge (discord_bridge.cpp & DiscordBridge.kt): Added CMake build configuration linking via Prefab to the Discord Social SDK. Implemented thread-safe JNI callbacks using recursive mutexes.
• Discord RPC Manager (DiscordRpcManager.kt): Handled OAuth2 PKCE authorization flow, token exchange (openid sdk.social_layer_presence scope), connection state mapping, debounced presence updates, and automatic disconnect after 1 minute of pause inactivity.
• Direct Discord App Auth Routing (AndroidManifest.xml & DiscordRpcManager.kt): Added package visibility queries (com.discord & discord://) to automatically route authorization requests directly to the installed Discord Android app before falling back to the web browser.
• Poster Artwork & Rich Presence Display:
  • Sets activity type to Watching (Watching Arvio).
  • Displays TMDB poster artwork inside the square image box (largeImage).
  • Displays movie titles cleanly with elapsed playback timers (XX:YY elapsed).
  • Displays TV show episode details (S1E1 - The Heirs of the Dragon).
  • Omits empty state strings to strictly comply with Discord SDK string length constraints (2–128 chars).
• Settings Screen Integration (SettingsScreen.kt): Added Discord Rich Presence account connection row to Settings -> Accounts with dynamic status indicators (Connected / Disconnected).

Screenshots

Movie Watch Activity (Supergirl)

• Header: Watching Arvio
• Details: Supergirl
• Poster Artwork: TMDB Movie Poster (Square)
• Timer: 11:42 elapsed

TV Show Watch Activity (House of the Dragon)

• Header: Watching Arvio
• Details: House of the Dragon
• State: S1E1 - The Heirs of the Dragon
• Poster Artwork: TMDB Series Poster (Square)
• Timer: 2:47 elapsed

Verification

• Verified native JNI library initialization and UpdateToken success on Android emulator (127.0.0.1:6555).
• Tested deep-link authentication redirect (arvio://discord/auth) and token persistence.
• Confirmed live presence updates, playback timers, poster rendering, and pause timeout logic.