feat(l1): drafts + tickets pages + coverage banner + seat counter widget

L1DraftsPage is a Phase 1 placeholder (AI drafts arrive in Phase 2).
L1TicketsPage replaces the stub with a status-filterable internal-tickets
queue. L1CoverageBanner renders inside L1RouteGuard so every /l1/* page
shows it for engineer-coverers (hidden for native L1). SeatCounterWidget
+ /api/seats.ts surface engineer + L1 seat usage from the /accounts/me/
seats endpoint (T9).

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

frontend/src/components/layout/L1RouteGuard.tsx

@@ -1,10 +1,18 @@
 import { Navigate } from 'react-router-dom'
 import { usePermissions } from '@/hooks/usePermissions'
+import { L1CoverageBanner } from '@/components/l1/L1CoverageBanner'
 
 export function L1RouteGuard({ children }: { children: React.ReactNode }) {
   const { canUseL1Surface } = usePermissions()
   if (!canUseL1Surface) {
     return <Navigate to="/" replace />
   }
-  return <>{children}</>
+  return (
+    <div className="flex flex-col h-full">
+      <L1CoverageBanner />
+      <div className="flex-1 min-h-0 flex flex-col">
+        {children}
+      </div>
+    </div>
+  )
 }