feat: Picture-in-Picture mode for touch devices

[chillpill244]

Summary

• PiP button added to the player controls row (touch devices only, Android 8+), positioned right after the aspect ratio button
• Three overlay action buttons (Replay 10s, Play/Pause, Forward 10s) rendered from the app's existing Material icon pack via CanvasDrawScope → Bitmap — no new XML drawables
• Icons scale proportionally to the PiP window size (estimated at 35% of screen width × 16:9), floored at 48dp
• BroadcastReceiver handles the three overlay actions tied to ExoPlayer's lifetime, registered as RECEIVER_NOT_EXPORTED
• Play/pause icon stays in sync with playback state via LaunchedEffect
• Subtitle text scaled to 40% when in PiP mode to stay readable in the small window
• ON_PAUSE lifecycle guard skips pausing ExoPlayer when entering PiP so video keeps playing
• Controls overlay hidden while in PiP mode
• All PiP logic gated on isTouchDevice() — TV devices are completely unaffected

Test plan

• Open any movie/show on a phone or tablet and tap the PiP button in the controls row
• Verify video continues playing in the PiP window
• Tap rewind / play-pause / forward in the PiP overlay and confirm ExoPlayer responds
• Tap the system expand button and confirm full-screen player is restored
• Verify subtitles appear smaller inside the PiP window
• Open on an Android TV device and confirm PiP button is absent and no PiP behaviour is triggered

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