feat(nix): add homeManagerModule for declarative settings

[roeybenarieh]

Summary

• Adds homeManagerModules.default flake output with a programs.ambxst.settings option
• Each attribute in settings maps to a JSON file at $XDG_CONFIG_HOME/ambxst/config/<name>.json
• Works with all config modules: bar, theme, compositor, system, performance, weather, desktop, lockscreen, prefix, dock, ai, workspaces, notch, overview

Usage

Add the module to your Home Manager config:

# In your flake.nix
inputs.ambxst.url = "github:Axenide/Ambxst";

# In your home-manager config
{ inputs, ... }: {
  imports = [ inputs.ambxst.homeManagerModules.default ];

  programs.ambxst = {
    enable = true;
    settings = {
      bar = {
        position = "top";
        use12hFormat = true;
      };
      theme = {
        roundness = 8;
        font = "Roboto";
      };
      compositor = {
        gapsIn = 4;
        blurEnabled = true;
      };
    };
  };
}

Notes

• Declared config files are managed as read-only symlinks into the Nix store. The GUI settings menu cannot persist changes to managed files — this is expected for declarative setups.
• Undeclared modules (e.g. ai, weather) are untouched and remain editable via the GUI.
• builtins.toJSON handles all JSON-compatible Nix values: nested attrsets, lists, strings, numbers, booleans, and null.

Closes #172

[roeybenarieh]

Some Notes:
I did everything with AI, I checked it looked ok and changed everything I knew could be better.
After changing the nix settings option, I told nix to run "ambxst reload | true" because by default the command wont return a 0 exit status code and nix need it to tell everything is Ok.
A more correct approach would be that the "ambxst reload" command would return the appropriate exit code.

Would love to hear your thoughts about is PR :-)

[128bytes8]

Seems like a good pull request, especially for homemanager.