feat: add BullMQ queue infrastructure and frontend job status hook

- apps/Backend/src/queue/: connection, queues, workers, processors
- apps/Frontend/src/hooks/use-job-status.ts: WebSocket job progress hook
- apps/Frontend/src/lib/socket.ts: shared Socket.IO singleton

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

apps/Backend/src/queue/workers/ocrWorker.ts

@@ -0,0 +1,55 @@
+import { Worker, Job } from "bullmq";
+import { redisConnection } from "../connection";
+import { OcrJobData } from "../queues";
+import { io } from "../../socket";
+import { runOcrProcessor } from "../processors/ocrProcessor";
+
+function emitJobUpdate(
+  socketId: string | undefined,
+  jobId: string,
+  status: "active" | "completed" | "failed",
+  payload: Record<string, any>
+) {
+  const event = "job:update";
+  const data = { jobId, jobType: "ocr", status, ...payload };
+  if (socketId && io) {
+    io.to(socketId).emit(event, data);
+  } else if (io) {
+    io.emit(event, data);
+  }
+}
+
+async function processOcrJob(job: Job<OcrJobData>) {
+  const { socketId, files } = job.data;
+  const jobId = job.id ?? job.name;
+
+  emitJobUpdate(socketId, jobId, "active", { message: "OCR processing started…" });
+
+  try {
+    const rows = await runOcrProcessor({ files });
+    emitJobUpdate(socketId, jobId, "completed", { result: { rows } });
+    return rows;
+  } catch (err: any) {
+    const errorMsg = err?.message ?? String(err);
+    emitJobUpdate(socketId, jobId, "failed", { error: errorMsg });
+    throw err;
+  }
+}
+
+export function startOcrWorker() {
+  const worker = new Worker<OcrJobData>("ocr-jobs", processOcrJob, {
+    connection: redisConnection,
+    concurrency: 2, // OCR service allows 2 concurrent
+  });
+
+  worker.on("completed", (job) => {
+    console.log(`[ocrWorker] job ${job.id} completed`);
+  });
+
+  worker.on("failed", (job, err) => {
+    console.error(`[ocrWorker] job ${job?.id} failed:`, err.message);
+  });
+
+  console.log("[ocrWorker] started");
+  return worker;
+}