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>

README.md

@@ -145,6 +145,11 @@ curl -fsSL https://git.0bin.in/thug0bin/headscale-tailscale-replacement/raw/bran
 wget -qO- https://git.0bin.in/thug0bin/headscale-tailscale-replacement/raw/branch/feature/working-headscale-setup/quick-install.sh | sudo bash
 ```
 
+### 기존 Tailscale 연결이 있는 경우 (강제 재등록)
+```bash
+curl -fsSL https://git.0bin.in/thug0bin/headscale-tailscale-replacement/raw/branch/feature/working-headscale-setup/quick-install.sh | sudo bash -s -- --force
+```
+
 ### 지원 OS
 - Ubuntu, Debian, CentOS, RHEL, Rocky Linux, Fedora, Arch Linux
 - 자동 Tailscale 설치 + Headscale 등록