feat: add structured logging to BullMQ queues and workers

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

packages/backend/src/queues/index.ts

@@ -1,8 +1,17 @@
 import { Queue } from "bullmq";
 import { redisConnectionOpts } from "./connection.js";
+import { logger } from "../lib/logger.js";
+
+const log = logger.child({ component: "queues" });
 
 export const mailQueue = new Queue("mail", { connection: redisConnectionOpts });
 
+mailQueue.on("error", (err) => {
+  log.error({ queue: "mail", err: err.message }, "Queue error");
+});
+
+log.info("Mail queue initialized");
+
 export const queues: Record<string, Queue> = {
   mail: mailQueue,
 };