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/team/accept/[token]/page.tsx

@@ -5,7 +5,12 @@ import { acceptInvite } from "@/app/actions/team"
 import { Logo } from "@/components/shared/logo"
 import { XCircle } from "lucide-react"
 
-export const metadata = { title: "Accept Team Invite" }
+// The URL carries a single-use invite token, so this page is noindex/nofollow
+// to keep tokens out of search results.
+export const metadata = {
+  title: "Accept team invite",
+  robots: { index: false, follow: false },
+}
 
 export default async function AcceptInvitePage({
   params,