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/core/network/relay_client.dart

@@ -75,6 +75,9 @@ class RelayClient {
 
   void _setState(RelayConnectionState s) {
     _state = s;
+    // Po dispose() je controller zavřený — pozdní přechod z doběhnutého
+    // _connect (zombie) by jinak hodil StateError do listenerů.
+    if (_stateController.isClosed) return;
     _stateController.add(s);
   }
 
@@ -292,6 +295,14 @@ class RelayClient {
     try {
       final channel = _transport.connectWs(Uri.parse('$_wsUrl/v1/ws'));
       await channel.ready;
+      // Během `ready` (přes Tor může viset dlouho) mohl přijít stop()/dispose()
+      // — Tor toggle nebo auto-lock. Bez téhle kontroly by vzniklo zombie
+      // autentizované spojení (relay má 2× jedno zařízení, DELIVERy padají do
+      // zavřených controllerů). Nezakládat ho, jen zavřít.
+      if (!_shouldRun) {
+        await channel.sink.close();
+        return;
+      }
       _channel = channel;
 
       // AUTH: výzva-odpověď podepsaná identity klíčem (XEdDSA)
@@ -322,9 +333,13 @@ class RelayClient {
             return;
           }
           if (frame.hasDeliver()) {
-            _deliverController.add(frame.deliver);
+            if (!_deliverController.isClosed) {
+              _deliverController.add(frame.deliver);
+            }
           } else if (frame.hasReceipt()) {
-            _receiptController.add(frame.receipt);
+            if (!_receiptController.isClosed) {
+              _receiptController.add(frame.receipt);
+            }
           }
         },
         onDone: _onDisconnected,