Desktop: UI scale preference (#3475)

* ui scale preference

* cleanup

* add update ui scale message to SIDE_EFFECT_FREE_MESSAGES

* fix mac title bar height

* hide UI preference section on web

* set % as unit of ui scale

frontend/src/messages.ts

@@ -319,6 +319,10 @@ export class UpdateViewportPhysicalBounds extends JsMessage {
 	readonly height!: number;
 }
 
+export class UpdateUIScale extends JsMessage {
+	readonly scale!: number;
+}
+
 // Rust enum `Key`
 export type KeyRaw = string;
 // Serde converts a Rust `Key` enum variant into this format with both the `Key` variant name (called `RawKey` in TS) and the localized `label` for the key
@@ -1766,6 +1770,7 @@ export const messageMakers: Record<string, MessageMaker> = {
 	UpdateToolShelfLayout,
 	UpdateViewportHolePunch,
 	UpdateViewportPhysicalBounds,
+	UpdateUIScale,
 	UpdateVisibleNodes,
 	UpdateWelcomeScreenButtonsLayout,
 	UpdateWirePathInProgress,