Phase 2 refinements: Firebase config, dev environment fixes, phase 3 requirement draft

- Integrated Firebase SDK in both Flutter apps (google-services, firebase_options)
- Fixed auth flow, API client, and pairing/status blocs for dev environment
- Added full Flutter project scaffolds (android, ios, web, etc.)
- Added phase 3 chat engine requirement document
- Added bugreport zip pattern to gitignore

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

backend/package.json

@@ -11,14 +11,15 @@
     "db:seed": "node src/db/seed.js"
   },
   "dependencies": {
-    "fastify": "^4.28.1",
+    "@fastify/cors": "^9.0.1",
     "@fastify/sensible": "^5.6.0",
+    "dotenv": "^16.4.5",
+    "fastify": "^4.28.1",
     "firebase-admin": "^12.2.0",
     "ioredis": "^5.4.1",
     "pg": "^8.12.0",
     "postgres": "^3.4.4",
-    "zod": "^3.23.8",
-    "dotenv": "^16.4.5"
+    "zod": "^3.23.8"
   },
   "devDependencies": {
     "@types/pg": "^8.11.6"