Add ability to choose script variant before execution

[emerick-biron]

🌟 Briefly describe the feature

Allow users to select which variant of a script to execute when multiple installation options exist.

📝 Detailed description

Some scripts in the community repository provide multiple installation variants under the same category (for example, Docker LXC scripts often include both a default and an Alpine Linux version).
Currently, only the first variant listed can be executed from the web UI — the others are displayed but cannot be selected or launched.

Requested improvement:

• When a script has multiple available variants, display all of them clearly in the script details view.
• Allow users to choose which one to execute before running the installation.
• Each variant should trigger its corresponding script file (e.g., install_default.sh, install_alpine.sh).

💡 Why is this useful?

This feature improves flexibility and usability for users who prefer lightweight or specialized environments (e.g., Alpine-based containers).
It prevents confusion when multiple scripts are visible but only one is functional, and ensures that all supported installation variants can be used directly from the web UI without manual editing or CLI intervention.

[michelroegl-brunner]

Yeah, sure. I totally forgot about it. This will be added!