feat: gamification queue with deduplication and unpublish revoke

- Add migration 0004: partial unique index on user_points (user_id, action, recording_id)
  for RECORDING_CREATE and RECORDING_FEATURED to prevent earn-on-republish farming
- Add revokePoints() to gamification lib; awardPoints() now uses onConflictDoNothing
- Add gamificationQueue (BullMQ) with 3-attempt exponential backoff
- Add gamification worker handling awardPoints, revokePoints, checkAchievements jobs
- Move all inline gamification calls in recordings + comments resolvers to queue
- Revoke RECORDING_CREATE points when a recording is unpublished (published → draft)
- Register gamification worker at server startup alongside mail worker

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

packages/backend/src/index.ts

@@ -17,6 +17,7 @@ import { redis } from "./lib/auth";
 import { logger } from "./lib/logger";
 import { migrate } from "drizzle-orm/node-postgres/migrator";
 import { startMailWorker } from "./queues/workers/mail";
+import { startGamificationWorker } from "./queues/workers/gamification";
 
 const PORT = parseInt(process.env.PORT || "4000");
 const UPLOAD_DIR = process.env.UPLOAD_DIR || "/data/uploads";
@@ -31,6 +32,7 @@ async function main() {
 
   // Start background workers
   startMailWorker();
+  startGamificationWorker();
   logger.info("Queue workers started");
 
   const fastify = Fastify({ loggerInstance: logger });