fix: calls — correct MSC4143 JWT flow + message order

Calls:
- JWT fetch now uses correct MSC4143 flow: get OpenID token from
  Synapse, then POST to /_matrix/livekit/jwt/sfu/get (was using
  GET with Bearer token to wrong path — returned 301→404)
- Error messages now visible for 3 seconds before popping screen
  (was flashing away instantly — user couldn't see failure reason)
- Voice vs video calls differentiated via ?video=0/1 query param
- Debug logging added to JWT flow for troubleshooting

Messages:
- Chat timeline now shows newest at bottom (standard behaviour).
  Was reversed twice: SDK returns newest-first, code reversed to
  oldest-first, then ListView(reverse:true) put oldest at bottom.
  Removed the extra .reversed — newest-first + reverse:true = correct.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

lib/features/calls/presentation/call_screen.dart

@@ -1,4 +1,4 @@
-// Version: 1.2.0 | Created: 2026-04-01 | Updated: 2026-04-02
+// Version: 1.2.1 | Created: 2026-04-01 | Updated: 2026-04-03
 // Full call screen with LiveKit video/audio.
 // - Remote video: full screen background
 // - Local video: picture-in-picture overlay (bottom right)
@@ -16,9 +16,14 @@ import '../domain/call_state.dart';
 import 'call_controller.dart';
 
 class CallScreen extends ConsumerStatefulWidget {
-  const CallScreen({super.key, required this.roomId});
+  const CallScreen({
+    super.key,
+    required this.roomId,
+    this.isVideo = true,
+  });
 
   final String roomId;
+  final bool isVideo;
 
   @override
   ConsumerState<CallScreen> createState() => _CallScreenState();
@@ -28,12 +33,11 @@ class _CallScreenState extends ConsumerState<CallScreen> {
   @override
   void initState() {
     super.initState();
-    // Start the call as soon as the screen opens.
-    // Using addPostFrameCallback so the provider is ready.
     WidgetsBinding.instance.addPostFrameCallback((_) {
-      ref
-          .read(callControllerProvider.notifier)
-          .joinCall(Uri.decodeComponent(widget.roomId), withVideo: true);
+      ref.read(callControllerProvider.notifier).joinCall(
+            Uri.decodeComponent(widget.roomId),
+            withVideo: widget.isVideo,
+          );
     });
   }
 
@@ -41,10 +45,25 @@ class _CallScreenState extends ConsumerState<CallScreen> {
   Widget build(BuildContext context) {
     final callState = ref.watch(callControllerProvider);
 
-    // Pop back automatically when call ends.
+    // On call ended: show error reason for 3 seconds before popping,
+    // so the user can see WHY the call failed.
     ref.listen<CallState>(callControllerProvider, (_, next) {
-      if (next is CallEnded && context.canPop()) {
-        context.pop();
+      if (next is CallEnded && mounted) {
+        final reason = next.reason;
+        if (reason != null && reason.isNotEmpty) {
+          ScaffoldMessenger.of(context).showSnackBar(
+            SnackBar(
+              content: Text(reason),
+              backgroundColor: Theme.of(context).colorScheme.error,
+              duration: const Duration(seconds: 3),
+            ),
+          );
+        }
+        // Delay pop so the user sees the error.
+        final nav = GoRouter.of(context);
+        Future.delayed(const Duration(seconds: 3), () {
+          if (mounted) nav.pop();
+        });
       }
     });