fix(build): ensure fresh Flutter build on each deploy

- Add flutter clean before build to prevent stale cached artifacts
- Add VERSION build arg for explicit cache busting
- Reorder build steps: clean → pub get → build_runner → health.json → build
- Replace deprecated dart:html with package:web in iframe_view_web.dart
- Add lint ignore to generate_health_json.dart

Fixes issue where Docker layer caching kept old main.dart.js
while regenerating health.json with new version number.

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

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

lib/features/front_hall/presentation/widgets/iframe_view_web.dart

@@ -1,8 +1,8 @@
-import 'dart:html' as html;
 import 'dart:ui_web' as ui_web;
 
 import 'package:flutter/material.dart';
 import 'package:url_launcher/url_launcher.dart';
+import 'package:web/web.dart' as web;
 
 /// Embedded iframe view for displaying external content (web only).
 ///
@@ -31,7 +31,7 @@ class IframeView extends StatefulWidget {
 
 class _IframeViewState extends State<IframeView> {
   late final String _viewType;
-  late html.IFrameElement _iframe;
+  late web.HTMLIFrameElement _iframe;
   bool _isLoading = true;
 
   @override
@@ -42,17 +42,18 @@ class _IframeViewState extends State<IframeView> {
   }
 
   void _createIframe() {
-    _iframe = html.IFrameElement()
+    _iframe = web.document.createElement('iframe') as web.HTMLIFrameElement
       ..src = widget.url
       ..style.border = 'none'
       ..style.width = '100%'
       ..style.height = '100%'
-      ..allow = 'fullscreen'
-      ..onLoad.listen((_) {
-        if (mounted) {
-          setState(() => _isLoading = false);
-        }
-      });
+      ..allow = 'fullscreen';
+
+    _iframe.onLoad.listen((_) {
+      if (mounted) {
+        setState(() => _isLoading = false);
+      }
+    });
 
     // Register the view factory
     ui_web.platformViewRegistry.registerViewFactory(