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/lib/main.dart

@@ -0,0 +1,120 @@
+import 'package:flutter/material.dart';
+import 'package:webview_flutter/webview_flutter.dart';
+
+void main() {
+  runApp(const MapApp());
+}
+
+class MapApp extends StatelessWidget {
+  const MapApp({super.key});
+
+  @override
+  Widget build(BuildContext context) {
+    return MaterialApp(
+      title: 'Fantasy Map Engine',
+      theme: ThemeData(
+        colorScheme: ColorScheme.fromSeed(seedColor: Colors.blue),
+        useMaterial3: true,
+      ),
+      home: const MapScreen(),
+    );
+  }
+}
+
+class MapScreen extends StatefulWidget {
+  const MapScreen({super.key});
+
+  @override
+  State<MapScreen> createState() => _MapScreenState();
+}
+
+class _MapScreenState extends State<MapScreen> {
+  late final WebViewController _controller;
+  double _waterLevel = 0.2;
+  bool _ready = false;
+
+  @override
+  void initState() {
+    super.initState();
+    _controller = WebViewController()
+      ..setJavaScriptMode(JavaScriptMode.unrestricted)
+      ..setBackgroundColor(const Color(0x00000000))
+      ..setNavigationDelegate(
+        NavigationDelegate(
+          onPageFinished: (String url) {
+            setState(() {
+              _ready = true;
+            });
+          },
+          onWebResourceError: (WebResourceError error) {
+            print('WebResourceError: ${error.description}');
+          },
+        ),
+      )
+      ..loadFlutterAsset('assets/www/engine/engine.html');
+  }
+
+  void _updateWaterLevel(double value) {
+    setState(() {
+      _waterLevel = value;
+    });
+
+    // Bridge call
+    if (_ready) {
+      _controller.runJavaScript("window.MapController.setWaterLevel($value)");
+    }
+  }
+
+  @override
+  Widget build(BuildContext context) {
+    return Scaffold(
+      body: Stack(
+        children: [
+          // WebGL Map Layer
+          WebViewWidget(controller: _controller),
+
+          // UI Overlay
+          Positioned(
+            bottom: 30,
+            left: 20,
+            right: 20,
+            child: Container(
+              padding: const EdgeInsets.all(16),
+              decoration: BoxDecoration(
+                color: Colors.black.withOpacity(0.6),
+                borderRadius: BorderRadius.circular(16),
+              ),
+              child: Column(
+                mainAxisSize: MainAxisSize.min,
+                children: [
+                  const Text(
+                    "Water Level",
+                    style: TextStyle(color: Colors.white, fontWeight: FontWeight.bold),
+                  ),
+                  Slider(
+                    value: _waterLevel,
+                    min: 0.0,
+                    max: 1.0,
+                    activeColor: Colors.blue,
+                    onChanged: _updateWaterLevel,
+                  ),
+                  Row(
+                    mainAxisAlignment: MainAxisAlignment.spaceEvenly,
+                    children: [
+                      ElevatedButton(
+                        onPressed: () {
+                          _controller.runJavaScript("window.MapController.rebuildMap('${DateTime.now().millisecondsSinceEpoch}')");
+                        },
+                        child: const Text("Rebuild"),
+                      ),
+                    ],
+                  )
+                ],
+              ),
+            ),
+          ),
+        ],
+      ),
+    );
+  }
+}