feat(app): redesigned interface, polls, drafts, forwarding and mentions

A new look across the app and a set of everyday messaging features.

Interface
- Home screen with Chats, Contacts and Settings tabs, a large title,
  search across chats and message text (diacritics-insensitive), filters
  and pinned chats.
- Conversation view with a translucent header and composer, grouped
  bubbles, author avatars and colours in groups, swipe to reply, an
  "N new messages" marker, a jump-to-latest button and in-chat search.
- Contact and group profiles: verification, shared photos, groups in
  common, disappearing messages, mute, block; members, admin badges,
  adding people, rename and leave for groups.
- Full-screen photo viewer that pages through the whole conversation.
- A stable avatar colour per person and a clearly visible read state.

Messaging
- Polls in chats and groups, single or multiple choice, with votes that
  can be changed or withdrawn; older clients see them as text.
- Drafts survive leaving a chat and show in the chat list.
- Forwarding of messages, photos, files and voice messages.
- Notes to self: a local-only, encrypted chat that never reaches the
  relay.
- @mentions in groups that notify even when the group is muted.
- Typing indicators sent as ephemeral messages, opt-in and mutual like
  read receipts.
- Delivery and read times per message and per group member.
- Profile photos, cropped, resized and stripped of metadata, delivered
  encrypted to contacts.
- Voice message playback at 1.5x and 2x.
- Call buttons in 1:1 chats and call log entries.

Fixes
- Muted groups no longer notify: muting was checked against the
  author's chat instead of the group.
- A blocked contact could unblock itself by changing its delivery
  address.
- Read receipts no longer regress to delivered when a late delivery
  receipt arrives.
- A message marked as failed corrects itself once it is delivered.
- Double ticks in groups now mean delivered to every member.

app/lib/app.dart

@@ -5,7 +5,9 @@ import 'package:flutter_riverpod/flutter_riverpod.dart';
 import 'package:go_router/go_router.dart';
 import 'package:sepot/core/l10n/l10n.dart';
 import 'package:sepot/core/theme/app_theme.dart';
+import 'package:sepot/core/calls/call_controller.dart';
 import 'package:sepot/features/auth/change_pin_screen.dart';
+import 'package:sepot/features/calls/call_screen.dart';
 import 'package:sepot/providers/messaging_provider.dart';
 import 'package:sepot/features/onboarding/onboarding_screen.dart';
 import 'package:sepot/features/onboarding/restore_screen.dart';
@@ -17,6 +19,8 @@ import 'package:sepot/features/conversation/conversation_screen.dart';
 import 'package:sepot/features/contacts/contact_verify_screen.dart';
 import 'package:sepot/features/contacts/contacts_screen.dart';
 import 'package:sepot/features/groups/create_group_screen.dart';
+import 'package:sepot/features/profile/contact_profile_screen.dart';
+import 'package:sepot/features/profile/group_profile_screen.dart';
 import 'package:sepot/features/settings/settings_screen.dart';
 import 'package:sepot/features/safety/report_screen.dart';
 import 'package:sepot/features/qr_pairing/qr_share_screen.dart';
@@ -62,6 +66,21 @@ final _router = GoRouter(
       path: '/conversation/:contactId',
       builder: (context, state) => ConversationScreen(
         contactId: state.pathParameters['contactId']!,
+        startSearch: state.uri.queryParameters['search'] == '1',
+      ),
+    ),
+    GoRoute(
+      path: '/contact/:contactId',
+      builder: (context, state) => ContactProfileScreen(
+        contactId: state.pathParameters['contactId']!,
+        fromChat: state.uri.queryParameters['from'] == 'chat',
+      ),
+    ),
+    GoRoute(
+      path: '/group/:groupId',
+      builder: (context, state) => GroupProfileScreen(
+        groupId: state.pathParameters['groupId']!,
+        fromChat: state.uri.queryParameters['from'] == 'chat',
       ),
     ),
     GoRoute(
@@ -72,6 +91,11 @@ final _router = GoRouter(
       path: '/create-group',
       builder: (context, state) => const CreateGroupScreen(),
     ),
+    GoRoute(
+      path: '/group/:groupId/add',
+      builder: (context, state) =>
+          CreateGroupScreen(addToGroupId: state.pathParameters['groupId']),
+    ),
     GoRoute(
       path: '/verify/:contactId',
       builder: (context, state) => ContactVerifyScreen(
@@ -101,6 +125,10 @@ final _router = GoRouter(
       path: '/change-pin',
       builder: (context, state) => const ChangePinScreen(),
     ),
+    GoRoute(
+      path: '/call',
+      builder: (context, state) => const CallScreen(),
+    ),
   ],
 );
 
@@ -116,6 +144,16 @@ class SepotApp extends ConsumerWidget {
     // null = systémový jazyk; než se volba načte z keystore, jede systém.
     final locale = ref.watch(localeProvider).valueOrNull;
 
+    // Příchozí i odchozí hovor otevře obrazovku hovoru odkudkoli.
+    ref.listen(callProvider.select((s) => s.phase), (previous, phase) {
+      final starting =
+          phase == CallPhase.incoming || phase == CallPhase.outgoing;
+      final path = _router.routerDelegate.currentConfiguration.uri.path;
+      if (starting && previous != phase && path != '/call') {
+        _router.push('/call');
+      }
+    });
+
     return _AutoLockGate(
       child: MaterialApp.router(
         onGenerateTitle: (context) => context.l10n.appTitle,