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/chat/presentation/chat_screen.dart

@@ -72,15 +72,17 @@ class _ChatScreenState extends ConsumerState<ChatScreen> {
           IconButton(
             icon: const Icon(Icons.call),
             tooltip: 'Voice call',
-            onPressed: () =>
-                context.push('/calls/${Uri.encodeComponent(_decodedRoomId)}'),
+            onPressed: () => context.push(
+              '/calls/${Uri.encodeComponent(_decodedRoomId)}?video=0',
+            ),
           ),
           // Video call
           IconButton(
             icon: const Icon(Icons.videocam_outlined),
             tooltip: 'Video call',
-            onPressed: () =>
-                context.push('/calls/${Uri.encodeComponent(_decodedRoomId)}'),
+            onPressed: () => context.push(
+              '/calls/${Uri.encodeComponent(_decodedRoomId)}?video=1',
+            ),
           ),
           IconButton(
             icon: const Icon(Icons.more_vert),