Restyle Quickshell settings inputs to match Omarchy aesthetic

Settings dialogs were rendering text/spin/combo controls with Qt's
default light style, which clashed with the dark Omarchy theme — black
text on dark fills, white dropdown popups, rounded corners, and a
pill-style toggle that didn't match the native StyleToggleRow switch.

- Style.qml: collapse all radius tokens to 0 so Noctalia-compat widgets
  inherit Omarchy's sharp-corner convention
- NToggle: rewrite to mirror the native 48x22 switch with accent fill
  and a sliding 16x16 thumb
- NComboBox: skin contentItem, indicator, popup, and delegate so the
  dropdown reads on dark themes
- NSpinBox: add a styled background, contentItem, and up/down indicators
- SettingsPanel calendar form + DynamicSettingsForm string field: drop
  default TextField chrome for the same translucent foreground fill used
  by WidgetCard, accent border on focus

default/quickshell/omarchy-shell/Commons/Style.qml

@@ -9,17 +9,18 @@ import "." as Commons
 QtObject {
   id: root
 
-  // Radii.
-  readonly property real radiusXXS: 1
-  readonly property real radiusXS: 2
-  readonly property real radiusS:  3
-  readonly property real radiusM:  4
-  readonly property real radiusL:  6
-  readonly property real radiusXL: 8
-  readonly property real iRadiusXS: 2
-  readonly property real iRadiusS:  3
-  readonly property real iRadiusM:  4
-  readonly property real iRadiusL:  6
+  // Radii. Omarchy uses sharp corners; all radius tokens collapse to 0 so
+  // Noctalia plugins inherit the same look as native widgets.
+  readonly property real radiusXXS: 0
+  readonly property real radiusXS: 0
+  readonly property real radiusS:  0
+  readonly property real radiusM:  0
+  readonly property real radiusL:  0
+  readonly property real radiusXL: 0
+  readonly property real iRadiusXS: 0
+  readonly property real iRadiusS:  0
+  readonly property real iRadiusM:  0
+  readonly property real iRadiusL:  0
 
   // Margins / paddings. Noctalia uses two parallel scales for margins (one
   // tighter, one looser); we map them to the same values.