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>

components/analytics/umami.tsx

@@ -0,0 +1,51 @@
+"use client";
+
+import Script from "next/script";
+import { ANALYTICS_PROXY_PATH, redactPayload, type UmamiPayload } from "@/lib/analytics";
+
+/** Name of the global the tracker's `data-before-send` hook resolves. */
+const BEFORE_SEND = "__umamiBeforeSend";
+
+declare global {
+  interface Window {
+    [BEFORE_SEND]?: (type: string, payload: UmamiPayload) => UmamiPayload;
+  }
+}
+
+// Registered at module scope rather than in an effect: the tracker reads
+// `window[BEFORE_SEND]` at send time, and this client chunk is evaluated before
+// next/script injects the tag, so there is no window in which an unredacted
+// event could slip out.
+if (typeof window !== "undefined") {
+  window[BEFORE_SEND] = (_type, payload) => redactPayload(payload);
+}
+
+/**
+ * Self-hosted Umami analytics.
+ *
+ * The tracker and its beacon are both served from this origin via the
+ * `/_a` rewrite in next.config.mjs. That matters for more than ad-blockers: the
+ * CSP in middleware.ts uses `'strict-dynamic'`, which makes browsers ignore host
+ * allowlists in `script-src` entirely — so allowlisting the Umami domain there
+ * would not have worked, and `connect-src 'self'` would still have blocked the
+ * beacon. Proxying keeps both same-origin and the policy unrelaxed.
+ */
+export function UmamiAnalytics({ websiteId }: { websiteId: string }) {
+  return (
+    <Script
+      src={`${ANALYTICS_PROXY_PATH}/script.js`}
+      strategy="afterInteractive"
+      data-website-id={websiteId}
+      // Point the beacon at the proxied path instead of letting the tracker
+      // derive it from its own src.
+      data-host-url={ANALYTICS_PROXY_PATH}
+      // Drop query strings and fragments at the source. /reset-password carries a
+      // live reset token in `?token=` and /sign-in carries `?redirect=`.
+      data-exclude-search="true"
+      data-exclude-hash="true"
+      data-before-send={BEFORE_SEND}
+      // Honour the browser's Do Not Track signal.
+      data-do-not-track="true"
+    />
+  );
+}