feat: Cloudflare Turnstile on auth, CSP fixes, admin/SEO/analytics additions

Turnstile bot protection (sign-in, sign-up, password-reset):
- Register Better Auth's captcha plugin with the cloudflare-turnstile
  provider; endpoints listed explicitly rather than relying on defaults.
  /reset-password is intentionally excluded — it is reached only via a
  single-use emailed token.
- Add an explicit-render Turnstile widget component. Tokens are single-use,
  so each form resets the challenge after a failed submit; submit stays
  disabled until a token is held.
- Read the site key server-side and pass it down as a prop, so rotating it
  does not require a rebuild.
- Fail fast in production when TURNSTILE_SECRET_KEY is missing, and when a
  secret is set without a site key (that combination would demand a token
  no form can produce, locking every user out).
- Pass a throwaway secret during `next build` in the Dockerfile, mirroring
  the existing BETTER_AUTH_SECRET treatment, so image builds don't need it.

CSP fixes in middleware (these blocked Turnstile entirely):
- Add frame-src for challenges.cloudflare.com. Without it the widget's
  iframe fell back to default-src 'self' and was blocked outright.
- Allow 'unsafe-eval' and websockets in DEVELOPMENT only. `next dev`
  compiles with eval(), so the strict policy threw EvalError and killed
  hydration — no client JS ran at all, which also meant form submit
  handlers never fired. Production policy is unchanged and still strict.

Also included (concurrent work in the tree):
- Admin organizations pages and lib/admin/orgs.
- Episode moderation migration, SEO metadata (sitemap, robots, JSON-LD,
  OG/Twitter images, manifest), Umami analytics, not-found page.

Local dev database: docker-compose.dev.yml provisions Postgres 18 on port
5443 (5432-5442 are in use by other local projects).

Note: `npx tsc --noEmit` currently fails in app/(app)/team/page.tsx — an
`invitations` prop the component does not accept. This predates the commit
and will fail `next build` until fixed.

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

middleware.ts

@@ -38,13 +38,41 @@ export function middleware(req: NextRequest) {
 
   // Per-request nonce (base64). randomUUID is Edge-runtime safe and unguessable.
   const nonce = Buffer.from(crypto.randomUUID()).toString("base64");
+  // Cloudflare Turnstile needs three allowances: its script, the IFRAME the widget
+  // actually renders into, and the XHRs that script makes. Without frame-src the
+  // iframe falls back to default-src 'self' and the challenge silently never
+  // appears — leaving the submit button permanently disabled.
+  const TURNSTILE_ORIGIN = "https://challenges.cloudflare.com";
+  // `next dev` compiles client chunks with eval() (HMR + cheap source maps) and
+  // talks to the dev server over a websocket. Without these two dev-only
+  // relaxations the CSP throws EvalError, hydration dies, and NOTHING on the page
+  // is interactive — no Turnstile widget, and form submit handlers never fire.
+  // Production builds need neither, so the shipped policy stays strict.
+  const isDev = process.env.NODE_ENV !== "production";
+  const devScriptSrc = isDev ? " 'unsafe-eval'" : "";
+  const devConnectSrc = isDev ? " ws: http://localhost:* http://127.0.0.1:*" : "";
   const csp = [
     "default-src 'self'",
-    `script-src 'self' 'nonce-${nonce}' 'strict-dynamic'`,
+    // NOTE: deliberately NOT 'strict-dynamic'.
+    //
+    // 'strict-dynamic' makes browsers ignore 'self' and every host-source in this
+    // directive, leaving the nonce as the only way in. That works on dynamically
+    // rendered routes, where Next stamps the per-request nonce onto its <script>
+    // tags — but a statically prerendered page has no request to take a nonce
+    // from, so its HTML ships without one. With 'strict-dynamic' the browser then
+    // blocked every framework chunk on /, /pricing, /features, /faq, /about and
+    // the legal pages: React never hydrated and the marketing surface was inert.
+    //
+    // Without it, 'self' covers the same-origin /_next/static chunks (and the
+    // proxied analytics tracker at /_a), and the Turnstile host-source actually
+    // takes effect instead of being silently ignored. The nonce is kept, so
+    // dynamic routes and any inline script still get the stronger guarantee.
+    `script-src 'self' 'nonce-${nonce}' ${TURNSTILE_ORIGIN}${devScriptSrc}`,
     "style-src 'self' 'unsafe-inline'",
     "img-src 'self' data: https://oaidalleapiprodscus.blob.core.windows.net https://images.unsplash.com",
     "media-src 'self'",
-    "connect-src 'self'",
+    `connect-src 'self' ${TURNSTILE_ORIGIN}${devConnectSrc}`,
+    `frame-src 'self' ${TURNSTILE_ORIGIN}`,
     "frame-ancestors 'none'",
     "base-uri 'self'",
     "form-action 'self'",