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/jitsi/presentation/welcome_screen.dart

@@ -1,4 +1,4 @@
-// Version: 1.0.0 | Created: 2026-04-05
+// Version: 1.0.1 | Created: 2026-04-05 | Updated: 2026-07-03
 // Welcome/landing screen — first thing unauthenticated users see.
 // Two paths: join a Jitsi conference (no login) or sign in for Matrix chat.
 
@@ -67,7 +67,7 @@ class _WelcomeScreenState extends State<WelcomeScreen> {
                       ),
                       const SizedBox(height: 8),
                       Text(
-                        'Chat and conference — all in one place',
+                        'Chat and conference, all in one place',
                         textAlign: TextAlign.center,
                         style: theme.textTheme.bodyMedium?.copyWith(
                           color: theme.colorScheme.onSurface.withAlpha(153),
@@ -84,7 +84,7 @@ class _WelcomeScreenState extends State<WelcomeScreen> {
                     isDark: isDark,
                     icon: Icons.videocam_outlined,
                     title: 'Join a Conference',
-                    subtitle: 'Paste your meeting link to join instantly — no account needed.',
+                    subtitle: 'Paste your meeting link to join instantly. No account needed.',
                     child: Column(
                       children: [
                         TextField(