feat: Implement Material Design 3 elevation and shadow effects

- Added global toggle for enabling M3 elevation & shadow effects
- Refactored various components to sync updated specs

quickshell/translations/settings_search_index.json

@@ -2400,6 +2400,23 @@
     ],
     "description": "0 = square corners"
   },
+  {
+    "section": "m3ElevationEnabled",
+    "label": "M3 Elevation & Shadows",
+    "tabIndex": 10,
+    "category": "Theme & Colors",
+    "keywords": [
+      "appearance",
+      "elevation",
+      "lift",
+      "material",
+      "m3",
+      "shadow",
+      "shadows",
+      "theme"
+    ],
+    "description": "Material Design 3 shadows and elevation on modals, popouts, and dialogs"
+  },
   {
     "section": "cursorSize",
     "label": "Cursor Size",