feat: upgrade to NixOS 25.11

- Update nixpkgs and home-manager to 25.11 release
- Update flake dependencies
- Migrate git config to settings attribute
- Replace deprecated packages (mpc-cli -> mpc, vaapiIntel -> intel-vaapi-driver)
- Fix system references to use stdenv.hostPlatform.system
- Add crowdsec module overrides
- Remove android-udev-rules from fuchsia
- Configure SSH with enableDefaultConfig = false
- Update zsh dotDir to use config.xdg.configHome

overlays/default.nix

@@ -19,7 +19,7 @@
   # be accessible through 'pkgs.unstable'
   unstable-packages = final: _prev: {
     unstable = import inputs.nixpkgs-unstable {
-      system = final.system;
+      system = final.stdenv.hostPlatform.system;
       config.allowUnfree = false;
     };
   };