feat: add Gitea Actions container and install scripts for Linux

[KohanMathers]

✍️ Description

Adds a new LXC script to install and configure a Gitea Act Runner (act_runner) on a Debian 12 container. The script interactively prompts the user for their Gitea instance URL, registration token, runner name, and labels, then downloads the latest release binary, registers the runner, and sets it up as a systemd service with Docker installed for job execution.

Script files are named with the -linux- infix (gitea-act-runner-linux-install.sh) intentionally — a Windows Gitea Act Runner container script is planned as a follow-up, and the naming convention leaves room for both to coexist cleanly.

🔗 Related Issue

Fixes #

✅ Prerequisites (X in brackets)

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

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🛠️ Type of Change (X in brackets)

• 🐞 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.

[MickLesk]

New Scripts Always against Dev Repo.