feat(#163): Add BullMQ dependencies

Added bullmq@^5.67.2 and @nestjs/bullmq@^11.0.4 to support job queue
management for the M4.2 Infrastructure milestone. BullMQ provides job
progress tracking, automatic retry, rate limiting, and job dependencies
over plain Valkey, complementing the existing ioredis setup.

Verified:
- pnpm install succeeds with no conflicts
- pnpm build completes successfully
- All packages resolve correctly in pnpm-lock.yaml

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

apps/api/package.json

@@ -26,6 +26,7 @@
   "dependencies": {
     "@anthropic-ai/sdk": "^0.72.1",
     "@mosaic/shared": "workspace:*",
+    "@nestjs/bullmq": "^11.0.4",
     "@nestjs/common": "^11.1.12",
     "@nestjs/core": "^11.1.12",
     "@nestjs/mapped-types": "^2.1.0",
@@ -45,6 +46,7 @@
     "adm-zip": "^0.5.16",
     "archiver": "^7.0.1",
     "better-auth": "^1.4.17",
+    "bullmq": "^5.67.2",
     "class-transformer": "^0.5.1",
     "class-validator": "^0.14.3",
     "gray-matter": "^4.0.3",