[Client] Make the link-connection gates port-aware and keyboard-safe

Second-pass review notes for the shared-deck link flow (Cockatrice#7244):

- FlowWidget arrow-key navigation is opt-in via addNavigableWidget, so
  combo/spin controls on the analytics flows keep their own arrow keys
- isConnectedTo and the open-deck/join-game preconditions compare the
  configured server port alongside the host, so a same-host/different-port
  link cannot resolve its share token or game id on the wrong instance
- the link sign-in dialog reuses an existing server entry's saved name
  instead of renaming it to the raw hostname
- skipStartupAutoConnect is cleared once the launch chain connects, so a
  later mid-session declined link cannot fire the startup fallback
- the plain-launch path of SingleInstanceManager no longer blocks on the
  primary's ACK
- link- and server-supplied text is html-escaped in the confirm prompts and
  shared-deck preview so markup cannot spoof the shown messages

cockatrice/src/interface/intents/intent_open_shared_deck.cpp

@@ -34,10 +34,15 @@ bool IntentOpenSharedDeck::checkPrecondition() const
     if (remoteClient->getStatus() != ClientStatus::StatusLoggedIn) {
         return false;
     }
-    // serverName() reflects the server the client was configured to connect to,
-    // which may differ from the actual TCP peer (e.g. when connecting through a
-    // proxy), so only the hostname is compared here.
-    return remoteClient->serverName().compare(context->serverContext.hostname, Qt::CaseInsensitive) == 0;
+    // serverName()/serverPort() reflect the server the client was configured
+    // to connect to, which may differ from the actual TCP peer (e.g. when
+    // connecting through a proxy), so compare those configured values. The
+    // share token must be resolved against the host the link named — a link to
+    // the same host on another port is a different server.
+    if (remoteClient->serverName().compare(context->serverContext.hostname, Qt::CaseInsensitive) != 0) {
+        return false;
+    }
+    return QString::number(remoteClient->serverPort()) == context->serverContext.port;
 }
 
 void IntentOpenSharedDeck::onPreconditionSatisfied()