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/app.dart

@@ -196,8 +196,12 @@ class _AutoLockGateState extends ConsumerState<_AutoLockGate>
     final kde = _router.state.uri.path;
     if (_bezZamku.contains(kde)) return;
 
+    // Zastavit službu a zamknout DB. messagingStartProvider ZÁMĚRNĚ
+    // neinvalidujeme tady — invalidace by ho eager-rebuildla ještě nad
+    // odemčeným storage (těsně před lock) a messaging by nastartoval nad DB,
+    // kterou hned zavíráme. Restart řeší odemykací obrazovky přes
+    // ref.invalidate(messagingStartProvider) až po úspěšném unlocku.
     await ref.read(messagingServiceProvider).stop();
-    ref.invalidate(messagingStartProvider);
     storage.lock();
     _router.go('/pin-lock');
   }