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/api/src/routes/files.rs

@@ -22,6 +22,7 @@ use crate::{error::ApiError, state::AppState};
 #[cfg(feature = "local-files")]
 use axum::{
     Json,
+    extract::Query,
     http::StatusCode,
     routing::{delete, post},
 };
@@ -143,13 +144,25 @@ async fn stream_file(
 // Rescan
 // ============================================================================
 
+#[cfg(feature = "local-files")]
+#[derive(Deserialize)]
+struct RescanQuery {
+    provider: Option<String>,
+}
+
 #[cfg(feature = "local-files")]
 async fn trigger_rescan(
     State(state): State<AppState>,
     CurrentUser(_user): CurrentUser,
+    Query(query): Query<RescanQuery>,
 ) -> Result<Json<serde_json::Value>, ApiError> {
-    let index = state.local_index.read().await.clone()
-        .ok_or_else(|| ApiError::not_implemented("no local files provider active"))?;
+    let map = state.local_index.read().await.clone();
+    let index = if let Some(id) = &query.provider {
+        map.get(id).cloned()
+    } else {
+        map.values().next().cloned()
+    };
+    let index = index.ok_or_else(|| ApiError::not_implemented("no local files provider active"))?;
     let count = index.rescan().await;
     Ok(Json(serde_json::json!({ "items_found": count })))
 }