feat: Extract hardcoded configs to environment variables

- Add environment variable configuration for backend and frontend
- Backend: DB_POOL_SIZE, JWT_EXPIRE_HOURS, timeout configs, directory paths
- Frontend: VITE_API_BASE_URL, VITE_UPLOAD_TIMEOUT, Whisper configs
- Create deployment script (scripts/deploy-backend.sh)
- Create 1Panel deployment guide (docs/1panel-deployment.md)
- Update DEPLOYMENT.md with env var documentation
- Create README.md with project overview
- Remove obsolete PRD.md, SDD.md, TDD.md (replaced by OpenSpec)
- Keep CORS allow_origins=["*"] for Electron EXE distribution

🤖 Generated with [Claude Code](https://claude.com/claude-code)

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

backend/app/database.py

@@ -10,7 +10,7 @@ def init_db_pool():
     global connection_pool
     connection_pool = pooling.MySQLConnectionPool(
         pool_name="meeting_pool",
-        pool_size=5,
+        pool_size=settings.DB_POOL_SIZE,
         host=settings.DB_HOST,
         port=settings.DB_PORT,
         user=settings.DB_USER,