feat: add selectable interface and code fonts (10 for each)

Adds separate UI and code font choices in settings
Applies font changes immediately
Lazy-loads selected remote fonts

packages/ui/src/lib/desktop.ts

@@ -135,6 +135,8 @@ export type DesktopSettings = {
   stickyUserHeader?: boolean;
   fontSize?: number;
   terminalFontSize?: number;
+  uiFont?: string;
+  monoFont?: string;
   padding?: number;
   cornerRadius?: number;
   inputBarOffset?: number;