feat: add PSA ticket export format and Quick-Start landing page

PSA Export:
- New "PSA / Ticket Note" export format optimized for ConnectWise
- Structured output: Problem, Steps Taken, Resolution, Time Spent, Notes
- Prominent "Copy for Ticket" button on session detail page
- 24 unit tests for PSA export generator

Quick-Start Landing:
- New default landing page with search-first UX
- Auto-focused search bar with debounced tree search
- "Continue Session" cards for active sessions
- "Recent Trees" section from session history
- Home nav item and logo links updated

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

frontend/src/router.tsx

@@ -9,6 +9,7 @@ import {
 } from '@/pages'
 
 // Lazy load heavy pages for code splitting
+const QuickStartPage = lazy(() => import('@/pages/QuickStartPage'))
 const TreeLibraryPage = lazy(() => import('@/pages/TreeLibraryPage'))
 const MyTreesPage = lazy(() => import('@/pages/MyTreesPage'))
 const TreeNavigationPage = lazy(() => import('@/pages/TreeNavigationPage'))
@@ -54,7 +55,11 @@ export const router = createBrowserRouter([
     children: [
       {
         index: true,
-        element: <Navigate to="/trees" replace />,
+        element: (
+          <Suspense fallback={<PageLoader />}>
+            <QuickStartPage />
+          </Suspense>
+        ),
       },
       {
         path: 'trees',