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/domain/src/repositories.rs

@@ -48,6 +48,7 @@ pub trait UserRepository: Send + Sync {
 
 #[derive(Debug, Clone)]
 pub struct ProviderConfigRow {
+    pub id: String,
     pub provider_type: String,
     pub config_json: String,
     pub enabled: bool,
@@ -57,8 +58,9 @@ pub struct ProviderConfigRow {
 #[async_trait]
 pub trait ProviderConfigRepository: Send + Sync {
     async fn get_all(&self) -> DomainResult<Vec<ProviderConfigRow>>;
+    async fn get_by_id(&self, id: &str) -> DomainResult<Option<ProviderConfigRow>>;
     async fn upsert(&self, row: &ProviderConfigRow) -> DomainResult<()>;
-    async fn delete(&self, provider_type: &str) -> DomainResult<()>;
+    async fn delete(&self, id: &str) -> DomainResult<()>;
 }
 
 /// Repository port for `Channel` persistence.