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>

.gitignore

@@ -50,3 +50,9 @@ logs/
 
 # Generated Excel records
 backend/record/
+
+# AI Assistant configuration
+.claude/
+openspec/
+AGENTS.md
+CLAUDE.md