feat: add local files provider with indexing and rescan functionality

- Implemented LocalFilesProvider to manage local video files.
- Added LocalIndex for in-memory and SQLite-backed indexing of video files.
- Introduced scanning functionality to detect video files and extract metadata.
- Added API endpoints for listing collections, genres, and series based on provider capabilities.
- Enhanced existing routes to check for provider capabilities before processing requests.
- Updated frontend to utilize provider capabilities for conditional rendering of UI elements.
- Implemented rescan functionality to refresh the local files index.
- Added database migration for local files index schema.

k-tv-backend/api/src/state.rs

@@ -25,6 +25,9 @@ pub struct AppState {
     #[cfg(feature = "auth-jwt")]
     pub jwt_validator: Option<Arc<JwtValidator>>,
     pub config: Arc<Config>,
+    /// Index for the local-files provider, used by the rescan route.
+    #[cfg(feature = "local-files")]
+    pub local_index: Option<Arc<infra::LocalIndex>>,
 }
 
 impl AppState {
@@ -105,6 +108,8 @@ impl AppState {
             #[cfg(feature = "auth-jwt")]
             jwt_validator,
             config: Arc::new(config),
+            #[cfg(feature = "local-files")]
+            local_index: None,
         })
     }
 }