This commit introduces significant performance optimizations and refactorings to the `UnifiedPlayerSheet`, focusing on animations, gesture handling, and rendering efficiency.

### Key Changes:

1.  **Optimized Player Sheet Animations:**
    *   Introduced a custom `rememberExpansionTransition` composable to manage animations tied to the sheet's expansion fraction. This replaces multiple `animate*AsState` calls with a more efficient, unified transition, reducing recompositions.
    *   The elevation (`playerAreaElevation`) and mini-player alpha (`miniAlpha`) are now driven by this unified transition.

2.  **Improved Drag Gesture Logic:**
    *   The vertical drag gesture handler (`detectVerticalDragGestures`) has been refactored for clarity and performance.
    *   It now uses `rememberUpdatedState` for values like `sheetCollapsedTargetY`, `sheetExpandedTargetY`, and `showPlayerContentArea`. This ensures the drag logic always references the latest values without needing to restart the gesture detector, making it more stable and efficient.

3.  **Conditional & Optimized `WavyMusicSlider`:**
    *   A new `isWaveEligible` parameter was added to `WavyMusicSlider`. This boolean, tied to the player sheet's expanded state, disables the wave effect and its underlying `rememberInfiniteTransition` when not visible. This significantly reduces CPU usage and invalidations when the player is collapsed.
    *   The wave drawing logic was improved to use `quadraticBezierTo` instead of `lineTo`, resulting in a much smoother sine wave animation with fewer drawing artifacts.

4.  **Album Art Prefetching Strategy:**
    *   Implemented two new composables, `PrefetchAlbumNeighbors` and `PrefetchAlbumNeighborsImg`, to proactively load album art for adjacent songs in the queue.
    *   Prefetching is triggered when the user starts expanding the player sheet or swipes the album carousel, ensuring cover art is ready before it comes into view and improving perceived performance.

5.  **General Code Cleanup:**
    *   Removed unused code, commented-out blocks, and unnecessary recomposition triggers throughout `UnifiedPlayerSheet.kt`.
    *   Added `key(song.id)` to items in `AlbumCarouselSection` to help Compose uniquely identify and manage items during recomposition.