convert mih web app from JS to WASm

mih_ui/lib/mih_helpers/mih_install_stub.dart

@@ -0,0 +1,3 @@
+void triggerWebInstall() {
+  // Safe no-op on Linux/Mobile
+}

mih_ui/lib/mih_helpers/mih_install_web.dart

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+import 'dart:js_interop';
+
+@JS('promptInstall')
+external void jsPromptInstall();
+
+@JS('isInstallPromptAvailable')
+external bool jsIsInstallPromptAvailable();
+
+void triggerWebInstall() {
+  if (jsIsInstallPromptAvailable()) {
+    jsPromptInstall();
+  }
+}

mih_ui/lib/mih_helpers/mih_utils_stub.dart

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+// Create this file anywhere, e.g., lib/mih_config/mih_web_utils_stub.dart
+void openWebWindow(String url, [String? target]) {
+  // Safe no-op or fallback on Linux (e.g., could use url_launcher if needed)
+}
+
+bool isWebStandalone() {
+  return false; // Always false on native Linux app
+}

mih_ui/lib/mih_helpers/mih_utils_web.dart

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+import 'package:web/web.dart' as web;
+
+void openWebWindow(String url, [String? target]) {
+  if (target != null) {
+    web.window.open(url, target);
+  } else {
+    web.window.open(url);
+  }
+}
+
+bool isWebStandalone() {
+  return web.window.matchMedia('(display-mode: standalone)').matches;
+}