refactor: simplify deployment - unified env and startup script

- Remove Docker deployment files (1panel doesn't use Docker)
- Unify .env files: .env.example -> .env (single config file)
- Merge start.sh and start-prod.sh into unified start.sh with --prod flag
- Update setup_dev_env.sh to use .env instead of .env.local
- Add DEPLOY.md with 1panel deployment guide

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

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

.gitignore

@@ -49,11 +49,9 @@ AGENTS.md
 CLAUDE.md
 
 # ===== Environment Variables =====
-# Local environment files (contain secrets, never commit)
-.env.local
-.env.*.local
-frontend/.env.local
-frontend/.env.*.local
+# 實際配置檔案包含敏感資訊，不追蹤
+.env
+frontend/.env
 
 # ===== Process ID Files =====
 .pid/