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/app/api/v1/upload/avatar-presign/route.ts

@@ -1,7 +1,7 @@
 import { NextRequest, NextResponse } from "next/server";
 import { z } from "zod";
 import { requireSession } from "@/lib/api-auth";
-import { createPresignedUploadUrl } from "@/lib/storage";
+import { createPresignedUploadPost } from "@/lib/storage";
 import { checkAndIncrementTierLimit, TierLimitError } from "@/lib/tiers";
 
 const ALLOWED_TYPES = ["image/jpeg", "image/png", "image/webp", "image/avif"] as const;
@@ -39,7 +39,7 @@ export async function POST(req: NextRequest) {
 
   const ext = contentType.split("/")[1] ?? "jpg";
   const key = `user-avatars/${session!.user.id}/${crypto.randomUUID()}.${ext}`;
-  const url = await createPresignedUploadUrl(key, contentType);
+  const { url, fields } = await createPresignedUploadPost(key, contentType, MAX_FILE_SIZE);
 
-  return NextResponse.json({ url, key });
+  return NextResponse.json({ url, fields, key });
 }

apps/web/app/api/v1/upload/presign/route.ts

@@ -1,7 +1,7 @@
 import { NextRequest, NextResponse } from "next/server";
 import { z } from "zod";
 import { requireSession } from "@/lib/api-auth";
-import { createPresignedUploadUrl } from "@/lib/storage";
+import { createPresignedUploadPost } from "@/lib/storage";
 import { db, recipes, eq, and } from "@epicure/db";
 import { checkAndIncrementTierLimit, TierLimitError } from "@/lib/tiers";
 
@@ -53,7 +53,7 @@ export async function POST(req: NextRequest) {
   const ext = contentType.split("/")[1] ?? "jpg";
   const folder = purpose === "review" ? "reviews" : "photos";
   const key = `recipes/${recipeId}/${folder}/${session!.user.id}-${crypto.randomUUID()}.${ext}`;
-  const url = await createPresignedUploadUrl(key, contentType);
+  const { url, fields } = await createPresignedUploadPost(key, contentType, MAX_FILE_SIZE);
 
-  return NextResponse.json({ url, key });
+  return NextResponse.json({ url, fields, key });
 }