feat(web): full SEO stack — metadata, JSON-LD, sitemap, robots, OG image

Ported and adapted from the BuildMyDiscord SEO setup:

- lib/seo.ts — single source for site constants, the FAQ data (shared by
  the rendered FAQ and the FAQPage schema so they never drift) and JSON-LD
  builders.
- Rich root metadata: title template, keywords, Open Graph, Twitter card,
  robots directives, canonical.
- JSON-LD: Organization + WebSite + SoftwareApplication sitewide, FAQPage
  on the landing page. No AggregateRating — there are no real reviews yet.
- app/robots.ts — allow all, explicit allow-list for AI answer-engine
  crawlers (GPTBot, ClaudeBot, PerplexityBot, …), disallow private routes.
- app/sitemap.ts — every public marketing + docs route.
- app/opengraph-image.tsx — monochrome on-brand 1200x630 share card.
- app/manifest.ts + public/llms.txt.
- Per-page metadata for pricing, changelog, security, privacy, terms,
  docs, templates and status.
- opengraph-image + apple-icon pinned to the edge runtime — next/og
  crashes during a Node-runtime prerender.

Verified: next build passes; /robots.txt, /sitemap.xml,
/manifest.webmanifest and /opengraph-image all generate.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

apps/web/app/sitemap.ts

@@ -0,0 +1,36 @@
+import { SITE_URL } from '@/lib/seo';
+import type { MetadataRoute } from 'next';
+
+type Entry = {
+  path: string;
+  priority: number;
+  changeFrequency: MetadataRoute.Sitemap[number]['changeFrequency'];
+};
+
+const ROUTES: Entry[] = [
+  { path: '/', priority: 1.0, changeFrequency: 'weekly' },
+  { path: '/pricing', priority: 0.9, changeFrequency: 'weekly' },
+  { path: '/templates', priority: 0.9, changeFrequency: 'daily' },
+  { path: '/docs', priority: 0.8, changeFrequency: 'weekly' },
+  { path: '/docs/concepts', priority: 0.7, changeFrequency: 'monthly' },
+  { path: '/docs/oauth', priority: 0.7, changeFrequency: 'monthly' },
+  { path: '/docs/authoring', priority: 0.7, changeFrequency: 'monthly' },
+  { path: '/docs/api-reference', priority: 0.7, changeFrequency: 'monthly' },
+  { path: '/docs/self-hosting', priority: 0.7, changeFrequency: 'monthly' },
+  { path: '/docs/faq', priority: 0.6, changeFrequency: 'monthly' },
+  { path: '/changelog', priority: 0.6, changeFrequency: 'weekly' },
+  { path: '/security', priority: 0.5, changeFrequency: 'monthly' },
+  { path: '/status', priority: 0.4, changeFrequency: 'weekly' },
+  { path: '/privacy', priority: 0.3, changeFrequency: 'yearly' },
+  { path: '/terms', priority: 0.3, changeFrequency: 'yearly' },
+];
+
+export default function sitemap(): MetadataRoute.Sitemap {
+  const now = new Date();
+  return ROUTES.map((r) => ({
+    url: `${SITE_URL}${r.path}`,
+    lastModified: now,
+    changeFrequency: r.changeFrequency,
+    priority: r.priority,
+  }));
+}