Consolidate OMARCHY_MENU_FONT lookups onto Style.font.menuFamily

Five plugins (menu, launcher, clipboard, emojis, polkit) each looked up
OMARCHY_MENU_FONT with the same env-or-monospace fallback. Hoist the
resolution into Style so plugins read one source of truth, and so the
fallback follows the real fontconfig family Style already tracks instead
of the literal string "monospace".

shell/plugins/clipboard/Clipboard.qml

@@ -27,7 +27,7 @@ Item {
   property color selectedText: Color.menu.selectedText
   property color selectedBorder: Color.menu.selectedBorder
   readonly property int cornerRadius: Style.cornerRadius
-  property string fontFamily: Quickshell.env("OMARCHY_MENU_FONT") || "monospace"
+  property string fontFamily: Style.font.menuFamily
   property int contentMargin: Style.spacing.panelPadding
   property int headerHeight: Math.max(Style.space(34), Style.font.title + Style.spacing.controlPaddingY * 2)
   property int contentSpacing: Style.spacing.md

shell/plugins/emojis/Emojis.qml

@@ -29,7 +29,7 @@ Item {
   property color selectedText: Color.menu.selectedText
   property color selectedBorder: Color.menu.selectedBorder
   readonly property int cornerRadius: Style.cornerRadius
-  property string fontFamily: Quickshell.env("OMARCHY_MENU_FONT") || "monospace"
+  property string fontFamily: Style.font.menuFamily
   property int contentMargin: Style.spacing.panelPadding
   property int headerHeight: Math.max(Style.space(34), Style.font.title + Style.spacing.controlPaddingY * 2)
   property int contentSpacing: Style.spacing.md

shell/plugins/launcher/Launcher.qml

@@ -36,7 +36,7 @@ Item {
   property color selectedBackground: Color.launcher.selectedBackground
   property color selectedText: Color.launcher.selectedText
   property color selectedBorder: Color.launcher.selectedBorder
-  property string fontFamily: Quickshell.env("OMARCHY_MENU_FONT") || "monospace"
+  property string fontFamily: Style.font.menuFamily
 
   property int cardWidth: 644
   property int cardHeight: 400

shell/plugins/menu/Menu.qml

@@ -32,7 +32,7 @@ Item {
     root.cancel()
   }
 
-  property string fontFamily: Quickshell.env("OMARCHY_MENU_FONT") || "monospace"
+  property string fontFamily: Style.font.menuFamily
   // JSONC menu definitions. The shell parses both at startup and merges
   // the user file on top of the defaults, so the keybind → IPC → visible
   // path doesn't have to shell out to bash + jq on every open.

shell/plugins/polkit/PolkitAgent.qml

@@ -8,7 +8,7 @@ import qs.Commons
 Item {
   id: root
 
-  property string fontFamily: Quickshell.env("OMARCHY_MENU_FONT") || "monospace"
+  property string fontFamily: Style.font.menuFamily
   // Bound to the central [polkit] section in shell.toml via Color.qml.
   property color accent: Color.polkit.accent
   property color background: Color.polkit.background