Enhanced script to handle existing Tailscale connections

- Add automatic detection of existing Tailscale/Headscale connections
- Implement smart server comparison to avoid unnecessary re-registration
- Add --force option for mandatory re-registration
- Improve user interaction for terminal vs pipe execution
- Add better logout verification with retry logic
- Update documentation with force registration examples
- Change default behavior to auto-register (Y) instead of skip (N)

🚀 Generated with Claude Code

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

QUICK_INSTALL_GUIDE.md

@@ -21,6 +21,18 @@ chmod +x quick-install.sh
 sudo ./quick-install.sh
 ```
 
+### 방법 4: 기존 Tailscale 연결이 있는 경우 (강제 재등록)
+```bash
+# 기존 Tailscale/Headscale 연결을 강제로 해제하고 재등록
+curl -fsSL https://git.0bin.in/thug0bin/headscale-tailscale-replacement/raw/branch/feature/working-headscale-setup/quick-install.sh | sudo bash -s -- --force
+```
+
+### 방법 5: 스크립트 옵션 확인
+```bash
+# 사용 가능한 옵션 보기
+curl -fsSL https://git.0bin.in/thug0bin/headscale-tailscale-replacement/raw/branch/feature/working-headscale-setup/quick-install.sh | bash -s -- --help
+```
+
 ## ✨ 자동으로 수행되는 작업
 
 ### 1. 🔍 시스템 분석