Add disc search (artist, album, track, slot) with view/play navigation

[c2b2pss]

Adds a search feature to find discs without paging through the whole grid.

• New /Search Razor Page — search by artist, album title, track title, or slot number
• Search icon added to the main navbar (next to settings)
• Search results link back to the main page via ?highlight= and ?play= query params,
  which scroll to and highlight the matching disc (with a pulsing animation), and
  optionally auto-play it once SignalR connects
• No changes to existing controllers, the SignalR hub, or JS files — self-contained addition

Tested against my own DVP-CX777ES with a ~400 disc library.