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/components/layout/AppLayout.tsx

@@ -47,6 +47,7 @@ export function AppLayout() {
   }, [mobileMenuOpen, handleKeyDown])
 
   const navItems = [
+    { path: '/', label: 'Home' },
     { path: '/trees', label: 'Trees' },
     { path: '/my-trees', label: 'My Trees' },
     { path: '/sessions', label: 'Sessions' },
@@ -70,7 +71,7 @@ export function AppLayout() {
               <Menu className="h-5 w-5" />
             </button>
 
-            <Link to="/trees" className="flex items-center gap-2">
+            <Link to="/" className="flex items-center gap-2">
               <BrandLogo size="sm" />
               <BrandWordmark size="sm" />
             </Link>
@@ -81,7 +82,7 @@ export function AppLayout() {
                   to={item.path}
                   className={cn(
                     'relative rounded-md px-3 py-2 text-sm font-medium transition-colors',
-                    location.pathname.startsWith(item.path)
+                    (item.path === '/' ? location.pathname === '/' : location.pathname.startsWith(item.path))
                       ? 'bg-accent text-accent-foreground'
                       : 'text-muted-foreground hover:bg-accent hover:text-accent-foreground'
                   )}
@@ -137,7 +138,7 @@ export function AppLayout() {
           {/* Drawer */}
           <nav className="absolute inset-y-0 left-0 w-72 border-r border-border bg-card shadow-xl animate-slide-in-left">
             <div className="flex h-16 items-center justify-between border-b border-border px-4">
-              <Link to="/trees" className="flex items-center gap-2">
+              <Link to="/" className="flex items-center gap-2">
                 <BrandLogo size="sm" />
                 <BrandWordmark size="sm" />
               </Link>
@@ -180,7 +181,7 @@ export function AppLayout() {
                     to={item.path}
                     className={cn(
                       'block rounded-md px-3 py-2.5 text-sm font-medium transition-colors',
-                      location.pathname.startsWith(item.path)
+                      (item.path === '/' ? location.pathname === '/' : location.pathname.startsWith(item.path))
                         ? 'bg-accent text-accent-foreground'
                         : 'text-muted-foreground hover:bg-accent hover:text-accent-foreground'
                     )}

frontend/src/components/session/ExportPreviewModal.tsx

@@ -8,7 +8,7 @@ interface ExportPreviewModalProps {
   onClose: () => void
   content: string
   filename: string
-  format: 'markdown' | 'text' | 'html'
+  format: 'markdown' | 'text' | 'html' | 'psa'
   onDownload: () => void
 }