Implement Standalone Android App via Flutter WebView

- Configured `vite.config.ts` for relative base path support.
- Initialized `mobile_app` Flutter project with `webview_flutter`.
- Added `assets/www` to Flutter assets configuration.
- Implemented `mobile_app/lib/main.dart` with WebView and Bridge API integration (Water Level Slider).
- Updated `.gitignore` for Flutter artifacts.
- Successfully built APK artifacts.

Co-authored-by: kliffdafunkfacekilla-arch <239708976+kliffdafunkfacekilla-arch@users.noreply.github.com>

mobile_app/assets/www/manifest.webmanifest

@@ -0,0 +1,42 @@
+{
+  "background_color": "#fff",
+  "display": "standalone",
+  "orientation": "any",
+  "name": "Azgaar's Fantasy Map Generator",
+  "short_name": "Azgaar's Fantasy Map Generator",
+  "description": "Web application generating interactive and highly customizable maps",
+  "scope": "/Fantasy-Map-Generator/",
+  "start_url": "/Fantasy-Map-Generator/?source=pwa",
+  "url": "https://azgaar.github.io/Fantasy-Map-Generator",
+  "icons": [
+    {
+      "src": "images/icons/icon_x512.png",
+      "sizes": "512x512",
+      "type": "image/png"
+    },
+    {
+      "src": "images/icons/maskable_icon_x512.png",
+      "sizes": "512x512",
+      "type": "image/png",
+      "purpose": "maskable"
+    },
+    {
+      "src": "images/icons/maskable_icon_x384.png",
+      "sizes": "384x384",
+      "type": "image/png",
+      "purpose": "maskable"
+    },
+    {
+      "src": "images/icons/maskable_icon_x192.png",
+      "sizes": "192x192",
+      "type": "image/png",
+      "purpose": "maskable"
+    },
+    {
+      "src": "images/icons/maskable_icon_x128.png",
+      "sizes": "128x128",
+      "type": "image/png",
+      "purpose": "maskable"
+    }
+  ]
+}