Add OpenTTD and Terraria support, improve config editors

- Add OpenTTD server integration (config editor, server card, API)
- Add Terraria server integration (config editor, API)
- Add legends to all config editors for syntax highlighting
- Simplify UserManagement: remove edit/delete buttons, add Discord avatars
- Add auto-logout on 401/403 API errors
- Update save button styling with visible borders

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

gsm-frontend/src/components/ZomboidConfigEditor.jsx

@@ -267,8 +267,8 @@ export default function ZomboidConfigEditor({ token }) {
             disabled={!hasChanges || saving}
             className={"flex items-center gap-2 px-4 py-2 rounded-lg transition-colors " +
               (hasChanges && !saving
-                ? 'bg-green-600 hover:bg-green-500 text-white'
-                : 'bg-gray-700 text-gray-500 cursor-not-allowed'
+                ? 'bg-green-600 hover:bg-green-500 text-white border-2 border-green-400'
+                : 'bg-gray-700 text-gray-500 cursor-not-allowed border-2 border-gray-600'
               )}
           >
             {saving ? (