feat(TRUEREF-0002): implement repository management service and REST API

Add RepositoryService with full CRUD, ID resolution helpers, input
validation, six SvelteKit API routes (GET/POST /api/v1/libs,
GET/PATCH/DELETE /api/v1/libs/:id, POST /api/v1/libs/:id/index), and
37 unit tests covering all service operations.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

src/lib/server/db/client.ts

@@ -0,0 +1,18 @@
+/**
+ * Provides a raw better-sqlite3 Database instance for use in services that
+ * need direct SQL access (not via Drizzle ORM).
+ */
+import Database from 'better-sqlite3';
+import { env } from '$env/dynamic/private';
+
+let _client: Database.Database | null = null;
+
+export function getClient(): Database.Database {
+	if (!_client) {
+		if (!env.DATABASE_URL) throw new Error('DATABASE_URL is not set');
+		_client = new Database(env.DATABASE_URL);
+		_client.pragma('journal_mode = WAL');
+		_client.pragma('foreign_keys = ON');
+	}
+	return _client;
+}