feat(qt): 2.1.x UI polish round — header selects, seekbar, shortcuts, per-tab filters

- Homologate the three Library header selects to the ambient Group style; Sort
  gains an arrow-down-up glyph, a "Sort" placeholder and an explicit Default,
  and every select's border clears when it returns to its default value.
- Seekbar fluidity: a drag scrubs locally and commits a single seek on release;
  the time readout is a floating opaque tooltip reparented to the overlay so the
  content-frame shadow no longer bleeds noise over it.
- Route the NowPlayingBar info button and title to the LOCAL track-info modal
  for a local row, so a local track no longer opens an empty Qobuz modal.
- App menu shows each entry's shortcut (muted, smaller, right-aligned, resolved
  per platform — Cmd on macOS, Ctrl elsewhere) and gains a Quit entry; the
  keyboard-shortcuts modal adds Close Window and Quit under Navigation, moves
  Immersive below Interface, and tightens row heights. i18n for Quit/Close
  Window across all eight locales.
- Persist each Library tab's filter toggles to disk, independently per tab.

cc

crates/qbz-i18n/translations/de/LC_MESSAGES/qbz-ui.po

@@ -7024,3 +7024,9 @@ msgstr "Nein"
 #: qbz-qt/qml/Main.qml
 msgid "Don't show again"
 msgstr "Nicht erneut anzeigen"
+
+msgid "Quit"
+msgstr "Beenden"
+
+msgid "Close Window"
+msgstr "Fenster schließen"

crates/qbz-i18n/translations/en/LC_MESSAGES/qbz-ui.po

@@ -2624,3 +2624,9 @@ msgstr "No"
 #: qbz-qt/qml/Main.qml
 msgid "Don't show again"
 msgstr "Don't show again"
+
+msgid "Quit"
+msgstr "Quit"
+
+msgid "Close Window"
+msgstr "Close Window"

crates/qbz-i18n/translations/es/LC_MESSAGES/qbz-ui.po

@@ -7030,3 +7030,9 @@ msgstr "No"
 #: qbz-qt/qml/Main.qml
 msgid "Don't show again"
 msgstr "No volver a mostrar"
+
+msgid "Quit"
+msgstr "Salir"
+
+msgid "Close Window"
+msgstr "Cerrar ventana"

crates/qbz-i18n/translations/fr/LC_MESSAGES/qbz-ui.po

@@ -7022,3 +7022,9 @@ msgstr "Non"
 #: qbz-qt/qml/Main.qml
 msgid "Don't show again"
 msgstr "Ne plus afficher"
+
+msgid "Quit"
+msgstr "Quitter"
+
+msgid "Close Window"
+msgstr "Fermer la fenêtre"

crates/qbz-i18n/translations/ja/LC_MESSAGES/qbz-ui.po

@@ -7005,3 +7005,9 @@ msgstr "いいえ"
 #: qbz-qt/qml/Main.qml
 msgid "Don't show again"
 msgstr "今後表示しない"
+
+msgid "Quit"
+msgstr "終了"
+
+msgid "Close Window"
+msgstr "ウィンドウを閉じる"

crates/qbz-i18n/translations/nl/LC_MESSAGES/qbz-ui.po

@@ -7012,3 +7012,9 @@ msgstr "Nee"
 #: qbz-qt/qml/Main.qml
 msgid "Don't show again"
 msgstr "Niet opnieuw tonen"
+
+msgid "Quit"
+msgstr "Afsluiten"
+
+msgid "Close Window"
+msgstr "Venster sluiten"

crates/qbz-i18n/translations/pt/LC_MESSAGES/qbz-ui.po

@@ -7022,3 +7022,9 @@ msgstr "Não"
 #: qbz-qt/qml/Main.qml
 msgid "Don't show again"
 msgstr "Não mostrar novamente"
+
+msgid "Quit"
+msgstr "Sair"
+
+msgid "Close Window"
+msgstr "Fechar janela"

crates/qbz-i18n/translations/ru/LC_MESSAGES/qbz-ui.po

@@ -7043,3 +7043,9 @@ msgstr "Нет"
 #: qbz-qt/qml/Main.qml
 msgid "Don't show again"
 msgstr "Больше не показывать"
+
+msgid "Quit"
+msgstr "Выход"
+
+msgid "Close Window"
+msgstr "Закрыть окно"