security: fix full audit findings (v0.32.0)

Full list of the audit's confirmed findings and their fixes:

- Stored XSS via unescaped JSON-LD on the public recipe page
  (app/r/[id]/page.tsx) — escape < before injecting.
- CSP allowed unsafe-eval in production — now dev-only (Next prod
  never eval()s; only its HMR does).
- avatarUrl accepted any URL with no ownership check — now takes an
  avatarKey issued by avatar-presign, validated server-side, same
  pattern as recipe/review photos.
- No session revocation on password change/reset — both now revoke
  other sessions (revokeOtherSessions: true, revokeSessionsOnPasswordReset).
- Rate-limit bypass via spoofable X-Forwarded-For — take the last
  (proxy-appended) hop instead of the first (client-supplied) one,
  matching the single-Traefik-hop topology.
- Webhook signing secrets stored plaintext — now AES-256-GCM
  encrypted like every other secret in this app, with a legacy-
  plaintext fallback for pre-existing rows (bare hex has no ":", our
  ciphertext format always does).
- Better Auth's own rate limiter defaulted to in-memory storage,
  ineffective across replicas — now backed by the same Redis as
  lib/rate-limit.ts (secondaryStorage), with storeSessionInDatabase
  explicit so session storage itself doesn't move as a side effect.
- Presigned upload URLs didn't bind the declared file size to the
  actual upload, letting a client under-declare size (and quota
  charge) then PUT an arbitrarily large object — switched to S3
  presigned POST with a signed content-length-range condition,
  enforced by the storage server itself.
- generateMetadata() on the recipe page skipped the visibility
  filter the page body uses, leaking a private recipe's title via
  <title> to any signed-in user with the id.
- Block/unblock had no rate limit, unlike follow/unfollow.
- AI quota was charged even when a user's own BYOK key was used
  (their own credentials/billing) — added an isByok flag through
  the config-resolution chain and skip the charge when set. Also
  wired BYOK into generate/generate-from-idea/translate/import-url,
  which never looked it up at all before.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

apps/web/lib/webhooks.ts

@@ -3,6 +3,16 @@ import { db } from "@epicure/db";
 import { webhooks, webhookDeliveries } from "@epicure/db";
 import { eq, and } from "@epicure/db";
 import { safeFetch } from "@/lib/validate-webhook-url";
+import { decrypt } from "@/lib/encrypt";
+
+// Secrets created before encryption-at-rest was added are a bare 64-char hex
+// string (crypto.randomBytes(32).toString("hex")) with no ":" separators —
+// encrypt()'s output is always "iv:authTag:ciphertext". Fall back to treating
+// the value as already-plaintext rather than a hard migration, since this is
+// only reached with a value this app itself generated (never user input).
+function decryptWebhookSecret(stored: string): string {
+  return stored.split(":").length === 3 ? decrypt(stored) : stored;
+}
 
 export const WEBHOOK_EVENTS = [
   "recipe.created",
@@ -27,7 +37,7 @@ export async function dispatchWebhook(userId: string, event: WebhookEvent, paylo
   await Promise.allSettled(
     filtered.map(async (hook) => {
       const body = JSON.stringify({ event, payload, timestamp: new Date().toISOString() });
-      const sig = crypto.createHmac("sha256", hook.secret).update(body).digest("hex");
+      const sig = crypto.createHmac("sha256", decryptWebhookSecret(hook.secret)).update(body).digest("hex");
       let statusCode = 0;
       let success = false;
       try {