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/(app)/u/[username]/loading.tsx

@@ -0,0 +1,32 @@
+import { Skeleton } from "@/components/ui/skeleton";
+import { SquareTileSkeleton } from "@/components/shared/skeletons";
+
+export default function UserProfileLoading() {
+  return (
+    <div className="max-w-4xl mx-auto space-y-10">
+      <div className="flex flex-col sm:flex-row gap-6 items-start sm:items-center">
+        <Skeleton className="h-24 w-24 shrink-0 rounded-full" />
+        <div className="flex-1 space-y-3">
+          <div className="space-y-2">
+            <Skeleton className="h-7 w-40" />
+            <Skeleton className="h-4 w-24" />
+          </div>
+          <Skeleton className="h-4 w-64" />
+          <div className="flex flex-wrap gap-2">
+            <Skeleton className="h-6 w-20 rounded-full" />
+            <Skeleton className="h-6 w-24 rounded-full" />
+            <Skeleton className="h-6 w-24 rounded-full" />
+          </div>
+        </div>
+      </div>
+      <div className="space-y-4">
+        <Skeleton className="h-6 w-24" />
+        <div className="grid grid-cols-2 sm:grid-cols-3 md:grid-cols-4 gap-4">
+          {Array.from({ length: 8 }).map((_, i) => (
+            <SquareTileSkeleton key={i} />
+          ))}
+        </div>
+      </div>
+    </div>
+  );
+}