Add support for root account execution without sudo

- Update script comments and documentation for root vs regular users
- Improve error message for missing root privileges
- Add separate command examples for root accounts (Proxmox, containers, etc.)
- Update README and installation guide with both sudo and non-sudo examples

🚀 Generated with Claude Code

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

README.md

@@ -137,17 +137,20 @@ git push origin main
 
 ### 빠른 설치 (권장)
 ```bash
+# 일반 사용자 계정
 curl -fsSL https://git.0bin.in/thug0bin/headscale-tailscale-replacement/raw/branch/feature/working-headscale-setup/quick-install.sh | sudo bash
-```
 
-### 또는 wget 사용
-```bash
-wget -qO- https://git.0bin.in/thug0bin/headscale-tailscale-replacement/raw/branch/feature/working-headscale-setup/quick-install.sh | sudo bash
+# root 계정 (Proxmox 등)
+curl -fsSL https://git.0bin.in/thug0bin/headscale-tailscale-replacement/raw/branch/feature/working-headscale-setup/quick-install.sh | bash
 ```
 
 ### 기존 Tailscale 연결이 있는 경우 (강제 재등록)
 ```bash
+# 일반 사용자
 curl -fsSL https://git.0bin.in/thug0bin/headscale-tailscale-replacement/raw/branch/feature/working-headscale-setup/quick-install.sh | sudo bash -s -- --force
+
+# root 계정
+curl -fsSL https://git.0bin.in/thug0bin/headscale-tailscale-replacement/raw/branch/feature/working-headscale-setup/quick-install.sh | bash -s -- --force
 ```
 
 ### 지원 OS