feat: implement background job system with queue, worker, scheduler, and handlers

- Add job queue abstraction (InMemoryQueue and Redis/BullMQ adapter)
- Add polling worker with retry logic and exponential backoff
- Add 6 job handlers: darkwatch.scan, voiceprint.batch, hometitle.scan,
  removebrokers.process, reports.generate, notifications.send
- Add cron-based scheduler with tier-appropriate frequencies
  (Basic/Plus/Premium)
- Add tRPC scheduler router for admin (runJobNow, getJobStatus, etc.)
- Add entry point with graceful shutdown support
- Achieve 100% test pass rate for new job system

web/src/server/jobs/handlers/index.ts

@@ -0,0 +1,34 @@
+import type { JobPayload, JobType } from "../queue";
+
+export type JobHandler<T extends JobType = JobType> = (payload: JobPayload[T]) => Promise<void>;
+
+export type HandlerMap = {
+  [K in JobType]: JobHandler<K>;
+};
+
+let handlers: HandlerMap | null = null;
+
+export function getHandlers(): HandlerMap {
+  if (!handlers) {
+    handlers = {
+      "darkwatch.scan": require("./darkwatch.scan").handler,
+      "voiceprint.batch": require("./voiceprint.batch").handler,
+      "hometitle.scan": require("./hometitle.scan").handler,
+      "removebrokers.process": require("./removebrokers.process").handler,
+      "reports.generate": require("./reports.generate").handler,
+      "notifications.send": require("./notifications.send").handler,
+    };
+  }
+  return handlers;
+}
+
+export function setHandlers(mock: Partial<HandlerMap>): void {
+  handlers = {
+    "darkwatch.scan": mock["darkwatch.scan"] ?? (async () => {}),
+    "voiceprint.batch": mock["voiceprint.batch"] ?? (async () => {}),
+    "hometitle.scan": mock["hometitle.scan"] ?? (async () => {}),
+    "removebrokers.process": mock["removebrokers.process"] ?? (async () => {}),
+    "reports.generate": mock["reports.generate"] ?? (async () => {}),
+    "notifications.send": mock["notifications.send"] ?? (async () => {}),
+  };
+}