feat: brand retheme to m8chat.au blues, fix black logo, v1.6.0+8

- m8logo.svg: inline fills (flutter_svg ignores <style> blocks; logo rendered black)
- theme.dart v2.0.0: purple -> site palette (#1265ED / #3B8BFF / navy darks)
- app_config.dart: appVersion 1.3.0 -> 1.6.0 (profile screen showed stale version)
- manifest.json: theme/background colours to match
- Remove em-dashes from user-visible UI strings (global style rule)
- chat_screen.dart: fix use_build_context_synchronously in _leaveRoom
- Deployed to app2.m8chat.au after full functionality audit (all green)

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

lib/features/profile/presentation/security_setup_dialog.dart

@@ -1,4 +1,4 @@
-// Version: 1.0.0 | Created: 2026-04-11
+// Version: 1.0.1 | Created: 2026-04-11 | Updated: 2026-07-03
 // Security setup dialog: drives the Matrix SDK Bootstrap to set up
 // SSSS, cross-signing, and online key backup in one flow.
 // For new users: creates everything, shows recovery key.
@@ -298,7 +298,7 @@ class _SecuritySetupDialogState extends State<_SecuritySetupDialog> {
               children: [
                 const Text(
                   'Your recovery key has been created. Save it somewhere '
-                  'safe — you will need it to restore your messages on '
+                  'safe. You will need it to restore your messages on '
                   'new devices.',
                 ),
                 const SizedBox(height: 16),
@@ -389,7 +389,7 @@ class _SecuritySetupDialogState extends State<_SecuritySetupDialog> {
               onPressed: () async {
                 await _restoreKeys();
               },
-              child: const Text('I saved it — continue'),
+              child: const Text('I saved it, continue'),
             ),
           ],
         _Phase.done => [