feat(ddns-updater): add DDNS-Updater LXC container script

[reptil1990]

Add bare-metal installation script for qdm12/ddns-updater with web UI on port 8000, supporting 60+ DNS providers.

✍️ Description

Add bare-metal LXC container script for ddns-updater - a lightweight universal DDNS updater with web UI supporting 60+ DNS providers including Cloudflare, Namecheap, GoDaddy, DuckDNS and more. Uses fetch_and_deploy_gh_release singlefile mode for the Go binary. Includes update function with data backup/restore.

🔗 Related PR / Issue

Link: #

✅ Prerequisites

• Self-review completed – Code follows project standards.
• Tested thoroughly – Changes work as expected.
• No breaking changes – Existing functionality remains intact.
• No security risks – No hardcoded secrets, unnecessary privilege escalations, or permission issues.

---

🛠️ Type of Change

• 🐞 Bug fix – Resolves an issue without breaking functionality.
• ✨ New feature – Adds new, non-breaking functionality.
• 💥 Breaking change – Alters existing functionality in a way that may require updates.
• 🆕 New script – A fully functional and tested script or script set.
• 🌍 Website update – Changes to website-related JSON files or metadata.
• 🔧 Refactoring / Code Cleanup – Improves readability or maintainability without changing functionality.
• 📝 Documentation update – Changes to README, AppName.md, CONTRIBUTING.md, or other docs.

---

🔍 Code & Security Review

• Follows Code_Audit.md & CONTRIBUTING.md guidelines
• Uses correct script structure (AppName.sh, AppName-install.sh, AppName.json)
• No hardcoded credentials

📋 Additional Information

• Resources: 1 CPU, 512MB RAM, 2GB Disk (Debian 13, unprivileged)
• Web UI on port 8000
• Config at /opt/ddns-updater/data/config.json
• Systemd service with environment variables for DATADIR, LISTENING_ADDRESS, LOG_LEVEL, PERIOD

---

📦 Application Requirements (for new scripts)

• The application is at least 6 months old (created 2018)
• The application is actively maintained (last release v2.9.0, Dec 2024)
• The application has 600+ GitHub stars (~1.9k stars)
• Official release tarballs are published (binary releases on GitHub)
• I understand that not all scripts will be accepted due to various reasons and criteria by the community-scripts ORG

🌐 Source

• GitHub: https://github.com/qdm12/ddns-updater
• Wiki: https://github.com/qdm12/ddns-updater/wiki

[reptil1990]

What is missing for a merge?

[michelroegl-brunner]

What is missing for a merge?

A second review approval. I tagged the other to have a look.