fix: Jitsi meeting join rendered blank page — call JitsiMeetExternalAPI with 'new'

- Bind JitsiMeetExternalAPI as extension type external constructor;
  the old external function binding invoked the ES6 class without 'new'
  and threw at runtime (silently, in release builds)
- joinMeeting: wait up to 5s for platform-view container div (post-frame
  race), build options via setProperty (jsify cannot carry DOM nodes),
  return success bool, log failures to browser console
- jitsi_screen: show 'Could not start the meeting' UI instead of blank
- v1.6.2+10, deployed to app2.m8chat.au

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

lib/features/jitsi/presentation/jitsi_screen.dart

@@ -1,4 +1,4 @@
-// Version: 1.2.0 | Created: 2026-04-05 | Updated: 2026-04-10
+// Version: 1.3.0 | Created: 2026-04-05 | Updated: 2026-07-04
 // Full-screen Jitsi meeting embedded via HtmlElementView (web platform view).
 
 import 'package:flutter/material.dart';
@@ -21,6 +21,7 @@ class _JitsiScreenState extends State<JitsiScreen> {
   late final JitsiLink? _link;
   bool _meetingStarted = false;
   bool _meetingEnded = false;
+  bool _meetingFailed = false;
 
   @override
   void initState() {
@@ -42,8 +43,9 @@ class _JitsiScreenState extends State<JitsiScreen> {
     _meetingStarted = true;
 
     // Post-frame so the HtmlElementView div is mounted in the DOM.
-    WidgetsBinding.instance.addPostFrameCallback((_) {
-      JitsiWebService.instance.joinMeeting(
+    // joinMeeting itself waits for the container div to appear.
+    WidgetsBinding.instance.addPostFrameCallback((_) async {
+      final ok = await JitsiWebService.instance.joinMeeting(
         roomName: _link.roomName,
         jwt: _link.jwt,
         onReadyToClose: () {
@@ -52,6 +54,9 @@ class _JitsiScreenState extends State<JitsiScreen> {
           }
         },
       );
+      if (!ok && mounted) {
+        setState(() => _meetingFailed = true);
+      }
     });
   }
 
@@ -111,6 +116,34 @@ class _JitsiScreenState extends State<JitsiScreen> {
       );
     }
 
+    if (_meetingFailed) {
+      return Scaffold(
+        appBar: AppBar(title: const Text('Conference')),
+        body: Center(
+          child: Padding(
+            padding: const EdgeInsets.all(32),
+            child: Column(
+              mainAxisAlignment: MainAxisAlignment.center,
+              children: [
+                const Icon(Icons.videocam_off_outlined, size: 48),
+                const SizedBox(height: 16),
+                const Text(
+                  'Could not start the meeting. '
+                  'Check your connection and try again.',
+                  textAlign: TextAlign.center,
+                ),
+                const SizedBox(height: 24),
+                ElevatedButton(
+                  onPressed: () => context.go('/rooms'),
+                  child: const Text('Back'),
+                ),
+              ],
+            ),
+          ),
+        ),
+      );
+    }
+
     // Render the Jitsi iframe and kick off the meeting once mounted.
     _startMeeting();