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>

docker-compose.yml

@@ -8,6 +8,11 @@ services:
       args:
         NEXT_PUBLIC_APP_URL: ${NEXT_PUBLIC_APP_URL}
         NEXT_PUBLIC_STRIPE_PUBLISHABLE_KEY: ${NEXT_PUBLIC_STRIPE_PUBLISHABLE_KEY}
+        NEXT_PUBLIC_TURNSTILE_SITE_KEY: ${NEXT_PUBLIC_TURNSTILE_SITE_KEY}
+        NEXT_PUBLIC_GOOGLE_SITE_VERIFICATION: ${NEXT_PUBLIC_GOOGLE_SITE_VERIFICATION:-}
+        NEXT_PUBLIC_BING_SITE_VERIFICATION: ${NEXT_PUBLIC_BING_SITE_VERIFICATION:-}
+        UMAMI_HOST_URL: ${UMAMI_HOST_URL:-}
+        UMAMI_WEBSITE_ID: ${UMAMI_WEBSITE_ID:-}
     image: podcast-distribution-ai:latest
     # Apply pending migrations on boot, then serve.
     command: sh -c "npx prisma migrate deploy && npm run start"
@@ -15,6 +20,11 @@ services:
     environment:
       STORAGE_DIR: /app/storage
       PORT: "3000"
+      # Also needed at run time, not just as build args: the app and admin route
+      # groups are `force-dynamic`, so the root layout re-reads these on every
+      # request rather than using the value baked into the prerendered HTML.
+      UMAMI_HOST_URL: ${UMAMI_HOST_URL:-}
+      UMAMI_WEBSITE_ID: ${UMAMI_WEBSITE_ID:-}
     volumes:
       - storage:/app/storage
     expose: