fix: reliable first-message send, QR routing, auto-lock recovery

Fixes reported by testers and found in an app review:

- First message right after install no longer fails. Before the app
  finished registering with the relay, the outgoing message could crash on
  a null delivery address. The profile field is now optional and the send
  path throws a clear "still connecting, try again shortly" error while
  registration completes in the background.
- The QR code and share link now appear only once the delivery address is
  ready. Previously a link generated before the first connection lacked
  routing, so the other side could not send the first message. The screen
  now shows a connecting state and reactively swaps in the QR when ready.
- Incomplete contact links are rejected on import instead of failing at
  first send, with a clear prompt to ask for a fresh link.
- Auto-lock no longer silences the app: after locking and unlocking,
  messaging is restarted (it previously stayed dead until app restart).
- Group messages are marked failed on a non-per-member send error instead
  of hanging in the "sending" state forever.
- Hardened the relay client against a rare duplicate connection when
  toggling Tor or locking mid-connect, and fromShareString now rejects a
  delivery address of the wrong length.
- Pin unifiedpush below 6.2.0 to drop the webcrypto dependency (its native
  framework lacks LC_ENCRYPTION_INFO and blocked the iOS upload).
- Skip Android release lint (network dependency check hangs on the build
  host and adds no value for a Flutter app).

app/lib/features/auth/pin_lock_screen.dart

@@ -6,6 +6,8 @@ import 'package:local_auth/local_auth.dart';
 import 'package:sepot/core/crypto/dek_wrap.dart';
 import 'package:sepot/core/l10n/l10n.dart';
 import 'package:sepot/core/theme/app_theme.dart';
+import 'package:sepot/providers/messaging_provider.dart';
+import 'package:sepot/providers/push_provider.dart';
 import 'package:sepot/providers/storage_provider.dart';
 import 'package:sepot/widgets/sepot_logo.dart';
 
@@ -43,6 +45,7 @@ class _PinLockScreenState extends ConsumerState<PinLockScreen> {
       );
       if (!ok) return; // uživatel zrušil → zůstává PIN
       await storage.unlockWithBiometrics();
+      _restartMessagingAfterUnlock();
       if (mounted) context.go('/chats');
     } catch (_) {
       // biometrie nedostupná/selhala — PIN je vždy fallback
@@ -211,6 +214,16 @@ class _PinLockScreenState extends ConsumerState<PinLockScreen> {
     });
   }
 
+  /// Auto-lock službu zastavil a storage zamkl; po odemčení je nutné
+  /// messaging znovu nastartovat. messagingStartProvider drží starou
+  /// „hotovou" hodnotu (start se sám neprovede) → invalidace ho přepočítá
+  /// nad odemčeným storage a spustí start() znovu (jinak žádný příjem ani
+  /// odesílání až do restartu appky).
+  void _restartMessagingAfterUnlock() {
+    ref.invalidate(messagingStartProvider);
+    ref.invalidate(pushInitProvider);
+  }
+
   Future<void> _verifyPin() async {
     setState(() => _isVerifying = true);
 
@@ -218,6 +231,7 @@ class _PinLockScreenState extends ConsumerState<PinLockScreen> {
       // „Ověření" PINu = Argon2id unwrap DEK + otevření SQLCipher DB.
       // Špatný PIN = GCM tag nesedí = DB zůstává nečitelná.
       await ref.read(storageProvider).unlockWithPin(_pin);
+      _restartMessagingAfterUnlock();
       if (mounted) context.go('/chats');
     } on WrongPinException {
       setState(() {