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/routes/settings/+page.server.ts

@@ -5,7 +5,9 @@ import { EmbeddingSettingsDtoMapper } from '$lib/server/mappers/embedding-settin
 import { EmbeddingSettingsService } from '$lib/server/services/embedding-settings.service.js';
 
 export const load: PageServerLoad = async () => {
-	const service = new EmbeddingSettingsService(getClient());
+	const db = getClient();
+	
+	const service = new EmbeddingSettingsService(db);
 	const settings = EmbeddingSettingsDtoMapper.toDto(service.getSettings());
 
 	let localProviderAvailable = false;
@@ -15,8 +17,30 @@ export const load: PageServerLoad = async () => {
 		localProviderAvailable = false;
 	}
 
+	// Read indexing concurrency setting
+	let indexingConcurrency = 2;
+	const concurrencyRow = db
+		.prepare<[], { value: string }>(
+			"SELECT value FROM settings WHERE key = 'indexing.concurrency'"
+		)
+		.get();
+	
+	if (concurrencyRow && concurrencyRow.value) {
+		try {
+			const parsed = JSON.parse(concurrencyRow.value);
+			if (typeof parsed === 'object' && parsed !== null && typeof parsed.value === 'number') {
+				indexingConcurrency = parsed.value;
+			} else if (typeof parsed === 'number') {
+				indexingConcurrency = parsed;
+			}
+		} catch {
+			indexingConcurrency = 2;
+		}
+	}
+
 	return {
 		settings,
-		localProviderAvailable
+		localProviderAvailable,
+		indexingConcurrency
 	};
 };