feat(ui): Phase 1 — shadcn/ui foundation and panel-based layout shell

- Install class-variance-authority, tailwindcss-animate, react-resizable-panels
- Add shadcn/ui CSS variables to index.css with AD-6 color tokens:
  light mode (white/gray backgrounds, indigo/blue accents)
  dark mode (deep charcoal/navy, muted teal/indigo accents)
- Update tailwind.config.ts with shadcn CSS var tokens and tailwindcss-animate plugin
- Create src/lib/utils.ts with cn() utility (clsx + twMerge)
- Add shadcn/ui Button and Separator components in src/components/ui/
- Rewrite Layout.tsx with 3-panel architecture:
  - Collapsible left sidebar with desktop collapse/expand and mobile slide-in
  - Resizable main content area via react-resizable-panels
  - Collapsible right details panel (hidden by default, opens on demand)
  - New header: logo, global search bar, theme toggle, profile placeholder
  - RightPanelContext for child views to open the details panel programmatically
- Migrate ThemeToggle to shadcn/ui Button styling (inline in Layout)
- All existing routes (Dashboard, Graph, Explorer, Console, API Docs) preserved
- Build passes clean: 0 TypeScript errors

Co-Authored-By: Paperclip <noreply@paperclip.ing>

Author: aksOps

src/main/frontend/package-lock.json

@@ -6,7 +6,10 @@
   "scripts": {
     "dev": "vite",
     "build": "tsc -b && vite build",
-    "preview": "vite preview"
+    "preview": "vite preview",
+    "test:e2e": "playwright test",
+    "test:e2e:headed": "playwright test --headed",
+    "test:e2e:report": "playwright show-report"
   },
   "dependencies": {
     "@monaco-editor/react": "^4.7.0",
@@ -16,19 +19,25 @@
     "@radix-ui/react-select": "^2.1.6",
     "@radix-ui/react-tooltip": "^1.1.8",
     "@types/d3": "^7.4.3",
+    "class-variance-authority": "^0.7.1",
     "clsx": "^2.1.1",
     "d3": "^7.9.0",
     "lucide-react": "^0.474.0",
     "react": "^18.3.1",
     "react-dom": "^18.3.1",
+    "react-resizable-panels": "^4.8.0",
     "react-router-dom": "^7.1.5",
     "swagger-ui-react": "^5.21.0",
-    "tailwind-merge": "^3.0.2"
+    "tailwind-merge": "^3.0.2",
+    "tailwindcss-animate": "^1.0.7"
   },
   "overrides": {
     "dompurify": "^3.3.3"
   },
   "devDependencies": {
+    "@axe-core/playwright": "^4.10.1",
+    "@playwright/test": "^1.51.1",
+    "@types/node": "^22.0.0",
     "@types/react": "^18.3.18",
     "@types/react-dom": "^18.3.5",
     "@types/swagger-ui-react": "^4.18.3",