feat: auth middleware, brain data layer, Valkey queue (P1-002, P1-003, P1-004)

Auth middleware (P1-002):
- DatabaseModule provides Db instance with graceful shutdown
- AuthModule mounts BetterAuth at /api/auth/* via toNodeHandler
- AuthGuard validates sessions via BetterAuth API
- CurrentUser decorator extracts user from request

Brain data layer (P1-003):
- CRUD repositories for projects, missions, tasks, conversations
- createBrain(db) factory returns all repositories
- Re-exports drizzle-orm query helpers from @mosaic/db to avoid
  duplicate package resolution

Queue (P1-004):
- ioredis-based Valkey client with createQueue/createQueueClient
- Enqueue/dequeue, pub/sub, queue length operations

Closes #11, Closes #12, Closes #13

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

packages/queue/package.json

@@ -16,7 +16,8 @@
     "test": "vitest run --passWithNoTests"
   },
   "dependencies": {
-    "@mosaic/types": "workspace:*"
+    "@mosaic/types": "workspace:*",
+    "ioredis": "^5.10.0"
   },
   "devDependencies": {
     "typescript": "^5.8.0",