Add keyboard shortcuts and QoL improvements to video player

[Th0rgal]

Summary

Adds comprehensive keyboard shortcuts and quality-of-life improvements to the video player:

• Speed control: [ and ] to cycle through playback speeds (0.5× to 2×)
• Subtitle cycling: S to toggle through subtitles or turn off
• Audio track cycling: A to switch between audio tracks
• Picture-in-Picture: I to toggle PiP mode
• Mark watched: M to toggle watched status during playback
• Volume feedback: Visual overlay showing volume level when adjusting with arrow keys
• Mouse movement: Auto-hide timer resets when mouse moves over player
• Double-click fullscreen: Double-clicking the video toggles fullscreen mode

Testing

Verified with Peekaboo automation testing:

• ✅ Space bar for play/pause works
• ✅ Volume control with visual overlay appears
• ✅ Speed shortcuts cycle correctly (1× → 2× → 1×)
• ✅ Fullscreen toggle with F key works
• ✅ Mouse movement detection functional

Remaining features need manual testing with videos containing subtitles/multiple audio tracks.

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Note

Enhances the video player with richer input controls, on-screen feedback, and better interaction handling.

• Adds keyboard shortcuts: [/] to change speed, s to cycle subtitles, a to cycle audio tracks, i to toggle PiP, m to toggle watched; keeps arrows for seek/volume and space for play/pause
• Introduces a transient volume HUD overlay that animates on volume changes
• Resets auto-hide controls timer on mouse movement via MouseTrackingPlayerView and onMouseMoved callback
• Supports double-click to toggle fullscreen; single-click toggles controls
• Extends PlayerController with speed stepping, subtitle/audio cycling, and selection state syncing
• Updates VideoPlayerRepresentable to use a custom AVPlayerView subclass for mouse tracking

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