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/connection.ts

@@ -0,0 +1,36 @@
+import Redis from "ioredis";
+
+const REDIS_URL = process.env.REDIS_URL || "redis://127.0.0.1:6379";
+
+/**
+ * Shared Redis client for BullMQ.
+ * BullMQ requires maxRetriesPerRequest: null.
+ *
+ * lazyConnect + connectTimeout mean: don't auto-connect on require(),
+ * and if Redis is unreachable, fail within 3 s instead of hanging forever.
+ */
+export const redisConnection = new Redis(REDIS_URL, {
+  maxRetriesPerRequest: null,
+  enableReadyCheck: false,
+  lazyConnect: true,
+  connectTimeout: 3_000,       // give up after 3 s if Redis is down
+  retryStrategy: (times) => {
+    // Stop retrying after 2 attempts so a missing Redis server is
+    // reported quickly rather than blocking the request indefinitely.
+    if (times > 2) return null;
+    return Math.min(times * 500, 1_000);
+  },
+});
+
+redisConnection.on("error", (err) => {
+  console.error("[Redis] connection error:", err.message);
+});
+
+redisConnection.on("connect", () => {
+  console.log("[Redis] connected at", REDIS_URL);
+});
+
+/** True once a successful connection has been established. */
+export let redisReady = false;
+redisConnection.on("ready", () => { redisReady = true; });
+redisConnection.on("close", () => { redisReady = false; });