chore: sync in-progress work across marketing, admin, API and tests

Snapshot of uncommitted work that had accumulated in the tree alongside
the Turnstile changes:

- marketing pages, SEO helpers (lib/seo.ts, lib/marketing/) and
  structured data
- admin billing actions and a per-user portfolio view, plus an admin
  error boundary
- rate limiting (lib/rate-limit.ts) applied across the /api/v1 surface
- CSP and proxy adjustments, accounting/webhook lib updates
- Playwright config and an e2e/unit test suite
- next bumped to ^16.3.4 with the lockfile regenerated
- generated AGENTS.md / CLAUDE.md

Authored by other sessions working in this tree; committed here so the
Turnstile work could be pushed without leaving the tree dirty.
Typecheck passes.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>

app/(marketing)/page.tsx

@@ -7,23 +7,23 @@ import { Testimonials } from "@/components/marketing/testimonials"
 import { PricingSection } from "@/components/marketing/pricing-section"
 import { FAQ } from "@/components/marketing/faq"
 import { CtaBanner } from "@/components/marketing/cta-banner"
+import { HomeStructuredData } from "@/components/marketing/structured-data"
 import { annualEnabled } from "@/lib/stripe/plans"
+import { pageMetadata } from "@/lib/seo"
 
-export const metadata = {
-  title: { absolute: "Property Management Software for Independent Landlords" },
-  description: "Track rent, manage maintenance, monitor leases, and keep expenses organised — all in one dashboard built for independent landlords. Free to start.",
-  alternates: { canonical: "/" },
-  openGraph: {
-    title: "Property management without the chaos",
-    description: "Track rent, manage maintenance, monitor leases, and keep expenses organised — all in one dashboard built for independent landlords. Free to start.",
-    url: "/",
-    type: "website",
-  },
-}
+export const metadata = pageMetadata({
+  title: "Property Management Software for Independent Landlords",
+  absoluteTitle: true,
+  description:
+    "Track rent, manage maintenance, monitor leases, and keep expenses organised — all in one dashboard built for independent landlords. Free to start.",
+  path: "/",
+  socialTitle: "Property management without the chaos",
+})
 
 export default function LandingPage() {
   return (
     <>
+      <HomeStructuredData />
       <Hero />
       <Marquee />
       <Problem />