feat(session): query enabled sources before providers (#85)

UserSessionManager now queries the user_sources table for enabled
sources before calling any provider. Providers receive the per-user
JSON config directly instead of querying the DB themselves, removing
their db dependency and eliminating redundant round-trips.

Co-authored-by: Ona <no-reply@ona.com>

apps/aelis-backend/src/session/feed-source-provider.ts

@@ -3,5 +3,5 @@ import type { FeedSource } from "@aelis/core"
 export interface FeedSourceProvider {
 	/** The source ID this provider is responsible for (e.g., "aelis.location"). */
 	readonly sourceId: string
-	feedSourceForUser(userId: string): Promise<FeedSource>
+	feedSourceForUser(userId: string, config: unknown): Promise<FeedSource>
 }