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- Revoke RECORDING_CREATE points when a recording is unpublished (published → draft)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/db/schema/gamification.ts

@@ -8,6 +8,7 @@ import {
   pgEnum,
   uniqueIndex,
 } from "drizzle-orm/pg-core";
+import { sql } from "drizzle-orm";
 import { users } from "./users";
 import { recordings } from "./recordings";
 
@@ -68,6 +69,11 @@ export const user_points = pgTable(
   (t) => [
     index("user_points_user_idx").on(t.user_id),
     index("user_points_date_idx").on(t.date_created),
+    uniqueIndex("user_points_unique_action_recording")
+      .on(t.user_id, t.action, t.recording_id)
+      .where(
+        sql`"action" IN ('RECORDING_CREATE', 'RECORDING_FEATURED') AND "recording_id" IS NOT NULL`,
+      ),
   ],
 );