feat: multi-instance provider support

- provider_configs: add id TEXT PK; migrate existing rows (provider_type becomes id)
- local_files_index: add provider_id column + index; scope all queries per instance
- ProviderConfigRow: add id field; add get_by_id to trait
- LocalIndex:🆕 add provider_id param; all SQL scoped by provider_id
- factory: thread provider_id through build_local_files_bundle
- AppState.local_index: Option<Arc<LocalIndex>> → HashMap<String, Arc<LocalIndex>>
- admin_providers: restructured routes (POST /admin/providers create, PUT/DELETE /{id}, POST /test)
- admin_providers: use row.id as registry key for jellyfin and local_files
- files.rescan: optional ?provider=<id> query param
- frontend: add id to ProviderConfig, update api/hooks, new multi-instance panel UX

k-tv-backend/infra/src/factory.rs

@@ -133,6 +133,7 @@ pub async fn build_local_files_bundle(
     transcode_dir: Option<std::path::PathBuf>,
     cleanup_ttl_hours: u32,
     base_url: String,
+    provider_id: &str,
 ) -> FactoryResult<LocalFilesBundle> {
     match pool {
         #[cfg(feature = "sqlite")]
@@ -143,7 +144,7 @@ pub async fn build_local_files_bundle(
                 transcode_dir: transcode_dir.clone(),
                 cleanup_ttl_hours,
             };
-            let idx = Arc::new(crate::LocalIndex::new(&cfg, sqlite_pool.clone()).await);
+            let idx = Arc::new(crate::LocalIndex::new(&cfg, sqlite_pool.clone(), provider_id.to_string()).await);
             let tm = transcode_dir.as_ref().map(|td| {
                 std::fs::create_dir_all(td).ok();
                 crate::TranscodeManager::new(td.clone(), cleanup_ttl_hours)