feat: add Sheet and Sidebar components for improved UI layout

- Introduced a new Sheet component for modal-like functionality with customizable content and animations.
- Implemented a Sidebar component with mobile responsiveness, state management, and keyboard shortcuts for toggling.
- Added Skeleton component for loading states and Tooltip component for enhanced user guidance.
- Created a useIsMobile hook to manage mobile view detection.
- Updated main entry point to render the new PlatformPage component.
- Enhanced styles for sidebar and scrollbar customization in CSS.
- Extended Tailwind configuration to include sidebar color variables for better theming.

frontend/src/app/platform/icon-map.tsx

@@ -0,0 +1,27 @@
+/**
+ * Map project icon ids to Lucide icons for the sidebar.
+ */
+
+import {
+  LayoutDashboard,
+  Folder,
+  FileStack,
+  Sparkles,
+  Box,
+  Layers,
+  type LucideIcon,
+} from 'lucide-react'
+import type { ProjectIconId } from './types'
+
+export const PROJECT_ICON_MAP: Record<ProjectIconId, LucideIcon> = {
+  layout: LayoutDashboard,
+  folder: Folder,
+  'file-stack': FileStack,
+  sparkles: Sparkles,
+  box: Box,
+  layers: Layers,
+}
+
+export function getProjectIcon(iconId: string): LucideIcon {
+  return PROJECT_ICON_MAP[iconId as ProjectIconId] ?? LayoutDashboard
+}