fix: mobile sidebar slide-in overlay with hamburger and panel toggle buttons

- LeftSidebar/RightSidebar: added className prop for 'open' class
- Topbar: wired hamburger onClick + added mobile-drawer-toggle button for right panel
- App.tsx: added SettingsModal import/state/render, passed className props to sidebars
- styles.css: mobile sidebars now fixed slide-in overlays (translateX) instead of display:none
- ui.types.ts: added className to RightSidebarProps, onOpenLeftDrawer/onOpenRightDrawer to TopbarProps
- Tested at 390px viewport: both sidebars slide in correctly, transform verified via DOM

frontend/src/types/ui.types.ts

@@ -65,6 +65,8 @@ export interface TopbarProps {
   onThemeToggle: () => void;
   theme: Theme;
   onOpenSettings?: () => void;
+  onOpenLeftDrawer?: () => void;
+  onOpenRightDrawer?: () => void;
 }
 
 export interface SettingsModalProps {
@@ -84,6 +86,7 @@ export interface LeftSidebarProps {
   selectedTemplate?: string | null;
   onTemplateSelect?: (templateName: string | null) => void;
   onCollapse?: () => void;
+  className?: string;
 }
 
 export interface CanvasAreaProps {
@@ -155,6 +158,7 @@ export interface RightSidebarProps {
   onKISuggestionClick?: (suggestion: KISuggestion) => void;
   kiLoading?: boolean;
   onUpdateElement?: (el: CADElement) => void;
+  className?: string;
 }
 
 export interface PropertiesPanelProps {