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/l1/L1CoverageBanner.tsx

@@ -0,0 +1,23 @@
+import { useNavigate } from 'react-router-dom'
+import { usePermissions } from '@/hooks/usePermissions'
+
+export function L1CoverageBanner() {
+  const perms = usePermissions()
+  const navigate = useNavigate()
+
+  // Show only for engineer-coverers / owners-stepping-in. Native L1 doesn't see it.
+  if (perms.isL1Tech) return null
+  if (!perms.canCoverL1) return null
+
+  return (
+    <div className="bg-info/10 text-info text-sm px-4 py-1.5 flex items-center justify-between border-b border-info/20">
+      <span>You're covering L1. Actions logged as coverage.</span>
+      <button
+        onClick={() => navigate('/')}
+        className="text-info hover:underline underline-offset-2"
+      >
+        Switch back →
+      </button>
+    </div>
+  )
+}