quickshell: replace macOS-style shell with standalone overview module

Swap the illogical-impulse-derived components for the upstream
quickshell-overview standalone module, update Hyprland keybinds
(Super+Tab overview, rofi launcher), refresh foot colors and
starship theme, and adjust related host/module wiring.

home/hypr/quickshell/common/widgets/StyledRectangularShadow.qml

@@ -0,0 +1,14 @@
+import QtQuick
+import QtQuick.Effects
+import ".."
+
+RectangularShadow {
+    required property var target
+    anchors.fill: target
+    radius: 20
+    blur: 0.9 * Appearance.sizes.elevationMargin
+    offset: Qt.vector2d(0.0, 1.0)
+    spread: 1
+    color: Appearance.colors.colShadow
+    cached: true
+}