feat: add processor service with Redis-backed job queue

- Introduced a new `processor` service in the Docker Compose setup to handle face matching jobs.
- Configured Redis as a job queue and state management system for processing searches.
- Updated the backend to enqueue jobs and manage user locks using Redis.
- Added environment variables for Redis configuration and runtime paths.
- Created technical design documentation for the processor service outlining architecture, queue model, and search lifecycle.
- Updated package.json and package-lock.json to include dependencies for BullMQ and ioredis in the processor workspace.
- Added sample PKL files for local testing in the `test_pkl` directory.

faceai/apps/backend/package.json

@@ -8,8 +8,11 @@
     "start": "node src/server.js"
   },
   "dependencies": {
+    "bullmq": "^5.48.1",
     "cookie-parser": "^1.4.7",
     "cors": "^2.8.5",
-    "express": "^4.21.2"
+    "express": "^4.21.2",
+    "ioredis": "^5.4.1",
+    "multer": "^2.0.0"
   }
 }