[DeckShare] Open shared decks via links with a gated preview flow (#7244)

* [DeckShare] Open shared decks via links with a gated preview flow

- Serialized url-chain dispatcher in IntentUrlParser; queue-drained
  urlChainFinished(bool) drives the startup auto-connect fallback
- Open-shared-deck intent with sequential download state machine,
  15s per-item timeout, partial-success offer, livable Cancel via
  ApplicationModal dlg_login_prompt interactive fallback
- Preview dialog: download progress label, share vocab sweep,
  palette-highlight selection frame, Space/Enter keyboard toggle,
  NoFocus checkbox, double-click tile opens immediately
- Confirm-before-server-migration with one-shot restore to the
  previous server on failed/cancelled chains (statusChanged settle
  deferral), hostname-only identity comparisons
- Skip credential link when already connected; arrow-key navigation
  in FlowWidget; card glows use palette highlight
- Address code-review M1-M4 and UI/UX QA blockers 1-2

* [DeckShare] End the open-shared-deck files with a trailing newline

* [DeckShare] Forward a dependency's cancellation as the owner's own

* [DeckShare] Let intent chains opt into the link sign-in dialog

* [DeckShare] Track link-intent chains per-run so each can restore its own session

* [Settings] Match a server on the exact host and port when adding it

* [DeckShare] Confirm the share link's target server before opening a deck

* [DeckShare] Reformat the link sign-in intent constructor

* [DeckShare] Time the share-list round trip and backstop silently-destroyed intent chains

* [Client] Drain a single-instance payload before its handlers read the socket again

* [Client] Treat a busy single-instance primary as alive instead of stealing its socket

* [DeckShare] Keep arrow-key navigation between flow items inside a scroll area

* [Client] Skip the startup connection when a macOS URL launch owns the connection

* [Client] Redact share secrets from activation URL logs

* [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

---------

Co-authored-by: Lukas Brübach <Bruebach.Lukas@bdosecurity.de>

cockatrice/src/interface/intents/intent_login.cpp

@@ -1,9 +1,14 @@
 #include "intent_login.h"
 
 #include "../../client/settings/cache_settings.h"
+#include "../widgets/dialogs/dlg_login_prompt.h"
 #include "libcockatrice/settings/servers_settings.h"
 
-IntentGetLoginCredentials::IntentGetLoginCredentials(ContextConnectToServer *_context) : Intent(), context(_context)
+#include <QDialog>
+
+IntentGetLoginCredentials::IntentGetLoginCredentials(ContextConnectToServer *_context,
+                                                     bool _promptForMissingCredentials)
+    : Intent(), context(_context), promptForMissingCredentials(_promptForMissingCredentials)
 {
 }
 
@@ -29,5 +34,46 @@ void IntentGetLoginCredentials::onPreconditionSatisfied()
 
 void IntentGetLoginCredentials::onPreconditionNotSatisfied()
 {
-    emitFailed(tr("No saved credentials for this server"));
+    // MainWindow::applyStartupDestination runs this intent on every launch for
+    // users whose startup tab is Server / Server Room; keep that path quiet, as
+    // it was before the link-driven sign-in dialog existed.
+    if (!promptForMissingCredentials) {
+        emitFailed(tr("No saved credentials for this server"));
+        return;
+    }
+
+    // No credentials saved for the target server: ask the user for them. They
+    // opt into saving them so later links to the same server connect directly.
+    const QString serverText = context->hostname + ":" + context->port;
+    DlgLoginPrompt dialog(serverText);
+    // ApplicationModal: the dialog has no parent (the intent is not a widget),
+    // so WindowModal would not actually block any other window.
+    dialog.setWindowModality(Qt::ApplicationModal);
+
+    if (dialog.exec() != QDialog::Accepted) {
+        emitCancelled();
+        return;
+    }
+
+    context->username = dialog.username();
+    context->password = dialog.password();
+
+    if (dialog.savePassword() && !context->username.isEmpty()) {
+        ServersSettings &servers = SettingsCache::instance().servers();
+        // The host may already be saved under a friendly name (e.g. a public-server
+        // list entry) with no credentials; reuse that name instead of overwriting
+        // it with the raw hostname when addNewServer updates the entry in place.
+        QString saveName = context->hostname;
+        const int existingIndex = servers.findServerIndex(context->hostname, context->port);
+        if (existingIndex >= 0) {
+            saveName =
+                servers.getValue(QString("saveName%1").arg(existingIndex), "server", "server_details").toString();
+            if (saveName.isEmpty()) {
+                saveName = context->hostname;
+            }
+        }
+        servers.addNewServer(saveName, context->hostname, context->port, context->username, context->password, true);
+    }
+
+    emitFinished();
 }