feat(TRUEREF-0022): complete iteration 0 — worker-thread indexing, parallel jobs, SSE progress

- Move IndexingPipeline.run() into Worker Threads via WorkerPool
- Add dedicated embedding worker thread with single model instance
- Add stage/stageDetail columns to indexing_jobs schema
- Create ProgressBroadcaster for SSE channel management
- Add SSE endpoints: GET /api/v1/jobs/:id/stream, GET /api/v1/jobs/stream
- Replace UI polling with EventSource on repo detail and admin pages
- Add concurrency settings UI and API endpoint
- Build worker entries separately via esbuild

src/hooks.server.ts

@@ -47,7 +47,29 @@ try {
 		embeddingService = new EmbeddingService(db, provider, activeProfile.id);
 	}
 
-	initializePipeline(db, embeddingService);
+	// Read database path from environment
+	const dbPath = process.env.DATABASE_URL;
+
+	// Read indexing concurrency setting from database
+	let concurrency = 2; // default
+	if (dbPath) {
+		const concurrencyRow = db
+			.prepare<[], { value: string }>(
+				"SELECT value FROM settings WHERE key = 'indexing.concurrency' LIMIT 1"
+			)
+			.get();
+		if (concurrencyRow) {
+			try {
+				const parsed = JSON.parse(concurrencyRow.value);
+				concurrency = parsed.value ?? 2;
+			} catch {
+				// If parsing fails, use default
+				concurrency = 2;
+			}
+		}
+	}
+
+	initializePipeline(db, embeddingService, { concurrency, dbPath });
 	console.log('[hooks.server] Indexing pipeline initialised.');
 } catch (err) {
 	console.error(