feat: enhance MapViewer with city selection and layout integration

- Added support for city selection in MapViewer, allowing users to click on cities to view details.
- Integrated map layout data to improve city rendering and positioning.
- Introduced SelectedCityPanel to display information about the selected city.
- Updated map asset handling with utility functions for building asset URLs.
- Enhanced state management in mapViewer store to track selected city.
- Improved responsiveness and styling of map components.
- Added new API endpoint for loading map layouts from legacy data.

app/game-frontend/src/env.d.ts

@@ -9,6 +9,7 @@ declare module '*.vue' {
 interface ImportMetaEnv {
     readonly VITE_GATEWAY_API_URL?: string;
     readonly VITE_GAME_API_URL?: string;
+    readonly VITE_GAME_ASSET_URL?: string;
     readonly VITE_GAME_PROFILE?: string;
 }