Adds a new "Experimental" settings screen, accessible from the main settings page. This screen is now hidden from the bottom navigation bar.

Refines the full player's loading placeholder UI:
- Replaces the generic music note icon with the app's monochrome logo.
- Updates placeholder shapes from sharp corners to rounded ones for a softer look.
- Adjusts spacing, padding, and dimensions of placeholder elements for better visual balance and alignment with the final UI.
- Changes the placeholder color derivation for improved theme consistency.

Updates icons in the "Experimental" settings screen for better clarity:
- `Delay album carousel`: `MusicNote` -> `ViewCarousel`
- `Delay song title`: `Visibility` -> `LinearScale`
- `Delay progress bar`: `PlayCircle` -> `Outlined.LinearScale`
- `Show full player placeholders`: `Visibility` -> `Rectangle`