[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

cockatrice/src/interface/widgets/dialogs/dlg_shared_decks_preview.cpp

@@ -0,0 +1,178 @@
+#include "dlg_shared_decks_preview.h"
+
+#include "../deck_share/shared_deck_preview_widget.h"
+#include "../general/layout_containers/flow_widget.h"
+
+#include <QCloseEvent>
+#include <QDateTime>
+#include <QDialogButtonBox>
+#include <QLabel>
+#include <QPushButton>
+#include <QVBoxLayout>
+#include <libcockatrice/card/database/card_database_querier.h>
+#include <libcockatrice/protocol/pb/serverinfo_deck_share_item.pb.h>
+
+DlgSharedDecksPreview::DlgSharedDecksPreview(QWidget *parent,
+                                             const CardDatabaseQuerier *querier,
+                                             const QString &shareName,
+                                             qint64 expiresAt,
+                                             const QString &serverText,
+                                             const QList<ServerInfo_DeckShareItem> &items)
+    : QDialog(parent)
+{
+    setWindowTitle(tr("Open shared decks"));
+    resize(700, 500);
+
+    auto *mainLayout = new QVBoxLayout(this);
+
+    auto *titleLabel = new QLabel(tr("Share: %1").arg(shareName.isEmpty() ? tr("Untitled") : shareName), this);
+    QFont titleFont = titleLabel->font();
+    titleFont.setBold(true);
+    titleFont.setPointSize(titleFont.pointSize() + 2);
+    titleLabel->setFont(titleFont);
+    mainLayout->addWidget(titleLabel);
+
+    if (!serverText.isEmpty()) {
+        mainLayout->addWidget(new QLabel(tr("From %1").arg(serverText), this));
+    }
+
+    if (expiresAt > 0) {
+        const QString expiryText = QDateTime::fromSecsSinceEpoch(expiresAt).toLocalTime().toString(Qt::TextDate);
+        mainLayout->addWidget(new QLabel(tr("This share link expires on %1").arg(expiryText), this));
+    }
+
+    downloadStatusLabel = new QLabel(this);
+    downloadStatusLabel->setVisible(false);
+    mainLayout->addWidget(downloadStatusLabel);
+
+    flowWidget = new FlowWidget(this, Qt::Horizontal, Qt::ScrollBarAlwaysOff, Qt::ScrollBarAsNeeded);
+    mainLayout->addWidget(flowWidget, 1);
+
+    for (const ServerInfo_DeckShareItem &item : items) {
+        QStringList tags;
+        for (const auto &tag : item.tags()) {
+            tags.append(QString::fromStdString(tag));
+        }
+
+        auto *tile = new SharedDeckPreviewWidget(
+            this, querier, QString::fromStdString(item.name()), QString::fromStdString(item.banner_card()),
+            QString::fromStdString(item.color_identity()), QString::fromStdString(item.game_format()), tags.join(", "));
+        flowWidget->addWidget(tile);
+        tiles.append(tile);
+        itemIds.append(item.id());
+    }
+
+    if (tiles.size() == 1) {
+        tiles.first()->setSelected(true);
+    }
+
+    auto *buttonBox = new QDialogButtonBox(this);
+    openSelectedButton = buttonBox->addButton(tr("Open selected"), QDialogButtonBox::AcceptRole);
+    openAllButton = buttonBox->addButton(tr("Open all"), QDialogButtonBox::ActionRole);
+    buttonBox->addButton(tr("Cancel"), QDialogButtonBox::RejectRole);
+    mainLayout->addWidget(buttonBox);
+
+    connect(buttonBox, &QDialogButtonBox::rejected, this, [this]() {
+        onCancel();
+        close();
+    });
+
+    // Esc calls QDialog::reject() directly (which hides the dialog without a
+    // close event), so route it through the same guarded cancel as the button.
+    connect(this, &QDialog::rejected, this, [this]() {
+        onCancel();
+        close();
+    });
+
+    connect(openSelectedButton, &QPushButton::clicked, this, &DlgSharedDecksPreview::openSelected);
+    connect(buttonBox, &QDialogButtonBox::clicked, this, [this, buttonBox](QAbstractButton *button) {
+        if (buttonBox->buttonRole(button) == QDialogButtonBox::ActionRole) {
+            openAll();
+        }
+    });
+
+    for (SharedDeckPreviewWidget *tile : tiles) {
+        connect(tile, &SharedDeckPreviewWidget::selectionToggled, this,
+                &DlgSharedDecksPreview::updateOpenSelectedEnabled);
+    }
+    for (int i = 0; i < tiles.size(); ++i) {
+        const int itemId = itemIds.at(i);
+        // Double-clicking a tile selects it and opens just that deck.
+        connect(tiles.at(i), &SharedDeckPreviewWidget::activated, this, [this, itemId]() {
+            resultEmitted = true;
+            setDownloading(true);
+            emit openRequested(QList<int>{itemId});
+        });
+    }
+    updateOpenSelectedEnabled();
+}
+
+QList<int> DlgSharedDecksPreview::selectedItemIds() const
+{
+    QList<int> selectedIds;
+    for (int i = 0; i < tiles.size(); ++i) {
+        if (tiles.at(i)->isSelected()) {
+            selectedIds.append(itemIds.at(i));
+        }
+    }
+    return selectedIds;
+}
+
+void DlgSharedDecksPreview::openSelected()
+{
+    const QList<int> selectedIds = selectedItemIds();
+    if (selectedIds.isEmpty()) {
+        return;
+    }
+    resultEmitted = true;
+    setDownloading(true);
+    emit openRequested(selectedIds);
+}
+
+void DlgSharedDecksPreview::openAll()
+{
+    resultEmitted = true;
+    setDownloading(true);
+    emit openRequested(itemIds);
+}
+
+void DlgSharedDecksPreview::setDownloading(bool downloading)
+{
+    if (downloadInProgress == downloading) {
+        return;
+    }
+    downloadInProgress = downloading;
+    downloadStatusLabel->setVisible(downloading);
+    for (SharedDeckPreviewWidget *tile : tiles) {
+        tile->setEnabled(!downloading);
+    }
+    openSelectedButton->setEnabled(!downloading);
+    openAllButton->setEnabled(!downloading);
+}
+
+void DlgSharedDecksPreview::setDownloadProgress(int done, int total, const QString &currentDeckName)
+{
+    if (!downloadInProgress) {
+        return;
+    }
+    downloadStatusLabel->setText(tr("Downloading deck %1 of %2: %3").arg(done).arg(total).arg(currentDeckName));
+}
+
+void DlgSharedDecksPreview::updateOpenSelectedEnabled()
+{
+    openSelectedButton->setEnabled(!selectedItemIds().isEmpty());
+}
+
+void DlgSharedDecksPreview::onCancel()
+{
+    if (!resultEmitted || downloadInProgress) {
+        resultEmitted = true;
+        emit cancelled();
+    }
+}
+
+void DlgSharedDecksPreview::closeEvent(QCloseEvent *event)
+{
+    onCancel();
+    QDialog::closeEvent(event);
+}