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/profile_screen.dart

@@ -1,4 +1,4 @@
-// Version: 1.4.0 | Created: 2026-04-01 | Updated: 2026-04-11
+// Version: 1.4.1 | Created: 2026-04-01 | Updated: 2026-07-03
 // Profile screen. Shows current user info and logout button.
 
 import 'package:flutter/material.dart';
@@ -89,7 +89,7 @@ class ProfileScreen extends ConsumerWidget {
               title: const Text('End-to-end encryption'),
               subtitle: Text(
                 client.encryptionEnabled
-                    ? 'Active — messages are encrypted'
+                    ? 'Active. Messages are encrypted'
                     : 'Not available in this browser',
               ),
               enabled: false,
@@ -108,7 +108,7 @@ class ProfileScreen extends ConsumerWidget {
                       if (restored && context.mounted) {
                         ScaffoldMessenger.of(context).showSnackBar(
                           const SnackBar(
-                            content: Text('Keys restored — reopen rooms '
+                            content: Text('Keys restored. Reopen rooms '
                                 'to see decrypted messages.'),
                           ),
                         );
@@ -121,7 +121,7 @@ class ProfileScreen extends ConsumerWidget {
               title: const Text('Security setup'),
               subtitle: Text(
                 client.encryption?.crossSigning.enabled == true
-                    ? 'Cross-signing active — device verified'
+                    ? 'Cross-signing active. Device verified'
                     : 'Set up cross-signing and key backup',
               ),
               enabled: client.encryptionEnabled,