feat(ui): style app menus and extract glossary dialog

- Add AppMenu and AppMenuItem so menu labels, mnemonics and shortcuts render consistently under org.kde.union
- Move the translation glossary into GlossaryDialog with add, remove and clear-all actions
- Regroup the translation preset and instructions settings layout

src/qml/HamburgerMenu.qml

@@ -29,19 +29,19 @@ ToolButton {
     ToolTip.visible: hovered && !menu.visible
     ToolTip.delay: Kirigami.Units.toolTipDelay
 
-    Menu {
+    AppMenu {
         id: menu
 
         y: root.inFooter ? -height - Kirigami.Units.largeSpacing : root.height + Kirigami.Units.largeSpacing
         modal: true
         dim: false
 
-        MenuItem {
+        AppMenuItem {
             action: root.actions.openFile
             visible: root.inFooter
             height: visible ? implicitHeight : 0
         }
-        MenuItem {
+        AppMenuItem {
             action: root.actions.openUrl
             visible: root.inFooter
             height: visible ? implicitHeight : 0
@@ -62,20 +62,20 @@ ToolButton {
             title: KI18n.i18nc("@title:menu", "Audio Track")
         }
         MenuSeparator {}
-        MenuItem { action: root.actions.translateSubtitle }
-        MenuItem { action: root.actions.toggleFullscreen }
-        MenuItem { action: root.actions.togglePlaylist }
-        MenuItem { action: root.actions.screenshot }
+        AppMenuItem { action: root.actions.translateSubtitle }
+        AppMenuItem { action: root.actions.toggleFullscreen }
+        AppMenuItem { action: root.actions.togglePlaylist }
+        AppMenuItem { action: root.actions.screenshot }
         MenuSeparator {}
-        MenuItem {
+        AppMenuItem {
             action: root.actions.configure
             visible: root.inFooter
             height: visible ? implicitHeight : 0
         }
-        MenuItem { action: root.actions.toggleMenuBar }
-        MenuItem { action: root.actions.about }
+        AppMenuItem { action: root.actions.toggleMenuBar }
+        AppMenuItem { action: root.actions.about }
         MenuSeparator {}
-        Menu {
+        AppMenu {
             title: KI18n.i18nc("@title:menu", "&More")
             FileMenu { actions: root.actions }
             ViewMenu { actions: root.actions }