fix: audit fixes — tier-quota bypass, webhook SSRF, auth hardening, pagination, a11y

Full audit (bugs/UI-UX/backend/feature-gap) turned up a money-leak AI quota
bypass, webhook SSRF, and a long tail of missing pagination/auth/a11y work.
Fixes land together since HANDOFF.md tracked them as one backlog.

- AI routes charge tier quota before generating; nutrition POST is author-only
- Webhook dispatch re-validates URL per delivery (SSRF/DNS-rebinding), treats
  redirects as failures; recipe.published now actually dispatches
- New indexes/unique constraints on recipes, meal-planning, comments FK cascade
- Recipe PUT/restore snapshot only inside the transaction, after validation
- Recipe DELETE cleans up S3 objects (recipe + review photos)
- Optimistic UI (favorite/star/follow/shopping-list) rolls back on failure
- Upload presign enforces file size cap + per-tier storage quota
- Route-level loading/error/not-found states across (app), admin, and root
- middleware.ts guards (app)/admin; requireAdmin checks DB role, not cached
  session; rate limiting applied to both session and API-key branches,
  bucketed per key; Stripe webhook dedupes by event id
- Pagination added to recipes, feed, profile, comments, pantry, admin tables
- Nav shows real avatar + profile link + dark-mode toggle; destructive actions
  standardized on AlertDialog
- Unsaved-changes guard + real ingredient/step validation on recipe form;
  canonical /recipes/[id] used in-app; next/image migration; aria-labels and
  alt text across icon buttons, avatars, recipe photos
- packages/api-types removed (zero callers, too drifted to safely rewire);
  openapi.ts and ai-keys error shape drift fixed; BYOK decrypt failures now
  surface instead of silently falling back to the platform key

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

apps/web/app/not-found.tsx

@@ -0,0 +1,35 @@
+export default function RootNotFound() {
+  return (
+    <div
+      style={{
+        display: "flex",
+        flexDirection: "column",
+        alignItems: "center",
+        justifyContent: "center",
+        gap: "1rem",
+        minHeight: "60vh",
+        padding: "2rem",
+        textAlign: "center",
+        fontFamily: "system-ui, sans-serif",
+      }}
+    >
+      <h1 style={{ fontSize: "1.5rem", fontWeight: 700 }}>Page not found</h1>
+      <p style={{ color: "#666", maxWidth: "28rem" }}>
+        The page you&apos;re looking for doesn&apos;t exist or may have been moved.
+      </p>
+      <a
+        href="/"
+        style={{
+          padding: "0.5rem 1rem",
+          borderRadius: "0.5rem",
+          background: "#111",
+          color: "#fff",
+          textDecoration: "none",
+          fontSize: "0.875rem",
+        }}
+      >
+        Back home
+      </a>
+    </div>
+  );
+}