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>

Dockerfile

@@ -3,7 +3,7 @@
 # Includes ffmpeg (audio stitching) + the full node_modules so the worker can run
 # via tsx and `prisma migrate deploy` can run on web startup.
 
-FROM node:20-bookworm-slim AS base
+FROM node:22-bookworm-slim AS base
 RUN apt-get update \
   && apt-get install -y --no-install-recommends ffmpeg openssl ca-certificates \
   && rm -rf /var/lib/apt/lists/*
@@ -23,13 +23,31 @@ COPY . .
 # provided as build args (Dokploy passes them from the env — see docker-compose.yml).
 ARG NEXT_PUBLIC_APP_URL
 ARG NEXT_PUBLIC_STRIPE_PUBLISHABLE_KEY
+ARG NEXT_PUBLIC_GOOGLE_SITE_VERIFICATION
+ARG NEXT_PUBLIC_BING_SITE_VERIFICATION
+ARG UMAMI_HOST_URL
+ARG UMAMI_WEBSITE_ID
+ARG NEXT_PUBLIC_TURNSTILE_SITE_KEY
 ENV NEXT_PUBLIC_APP_URL=$NEXT_PUBLIC_APP_URL
 ENV NEXT_PUBLIC_STRIPE_PUBLISHABLE_KEY=$NEXT_PUBLIC_STRIPE_PUBLISHABLE_KEY
+ENV NEXT_PUBLIC_GOOGLE_SITE_VERIFICATION=$NEXT_PUBLIC_GOOGLE_SITE_VERIFICATION
+ENV NEXT_PUBLIC_BING_SITE_VERIFICATION=$NEXT_PUBLIC_BING_SITE_VERIFICATION
+# Not NEXT_PUBLIC_, but still needed at build time: the root layout is statically
+# rendered, so the website id is baked into the prerendered HTML.
+ENV UMAMI_HOST_URL=$UMAMI_HOST_URL
+ENV UMAMI_WEBSITE_ID=$UMAMI_WEBSITE_ID
+ENV NEXT_PUBLIC_TURNSTILE_SITE_KEY=$NEXT_PUBLIC_TURNSTILE_SITE_KEY
 # A throwaway BETTER_AUTH_SECRET, scoped to THIS command only (not a persisted ENV
 # layer), satisfies the prod-secret guard in lib/auth/auth.ts during `next build`.
 # Must be >= 32 chars (and not a known placeholder) to pass that guard; the real
 # secret is injected at run time and is never baked into the bundle.
-RUN BETTER_AUTH_SECRET=build-time-placeholder-not-a-real-secret npm run build
+# TURNSTILE_SECRET_KEY gets the same treatment for the Turnstile guard in
+# lib/auth/auth.ts: a throwaway value satisfies it during `next build`, while the
+# real secret is injected at run time and never baked into the image. (The SITE
+# key is not a secret and is a real build arg above.)
+RUN BETTER_AUTH_SECRET=build-time-placeholder-not-a-real-secret \
+    TURNSTILE_SECRET_KEY=build-time-placeholder-not-a-real-secret \
+    npm run build
 
 # ---- runtime ----
 FROM base AS runner
@@ -46,6 +64,10 @@ COPY --from=build /app ./
 # unaffected: `next start` serves prebuilt output and never relies on the throw.
 RUN cp node_modules/server-only/empty.js node_modules/server-only/index.js
 RUN mkdir -p /app/storage/mp3 /app/storage/art /app/storage/exports
+# Drop root. `node` (uid 1000) ships with the official image. /app/storage is the
+# only path written at run time, so it (and the Next.js cache) must be owned by it.
+RUN chown -R node:node /app/storage /app/.next
+USER node
 EXPOSE 3000
 # Default = web; the worker service overrides this command in docker-compose.yml.
 CMD ["npm", "run", "start"]