feat: per-category email prefs, admin ops webhooks, per-user feature toggles (v0.61.0)

- Notification email preferences: every push category (follow, comment,
  reply, reaction, rating, mention, leftoverExpiring, shoppingList) now has
  an independent email toggle, plus a Weekly Digest toggle. Previously email
  sent unconditionally whenever the recipient had one; now gated the same
  way push already was. The weekly-digest cron route excludes opted-out
  users.

- Admin-only site-wide webhooks (Admin → Webhooks): new signups, support
  tickets, and reports filed can now fire an HMAC-signed HTTP webhook
  (Slack/Discord/ops alerting), independent of the existing per-user
  webhooks (which stay scoped to a user's own recipe/meal-plan/shopping-list
  events). Signing/delivery logic factored into lib/webhook-delivery.ts and
  shared by both dispatchers instead of duplicated.

- Settings → Features: users can hide Nutrition, Pantry, Meal Plan,
  Shopping Lists, Collections, or Messages from their own nav. Purely
  cosmetic — hidden pages stay reachable by direct link, nothing is
  access-restricted.

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

apps/web/lib/webhook-delivery.ts

@@ -0,0 +1,47 @@
+import crypto from "crypto";
+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).
+export function decryptWebhookSecret(stored: string): string {
+  return stored.split(":").length === 3 ? decrypt(stored) : stored;
+}
+
+/**
+ * Signs and POSTs a single webhook payload. Shared by the per-user
+ * (`lib/webhooks.ts`) and admin (`lib/admin-webhooks.ts`) dispatchers so the
+ * signing/delivery mechanics — which are security-relevant — live in exactly
+ * one place instead of two copies that could drift.
+ */
+export async function deliverWebhook(
+  url: string,
+  secret: string,
+  event: string,
+  payload: object
+): Promise<{ statusCode: number; success: boolean }> {
+  const body = JSON.stringify({ event, payload, timestamp: new Date().toISOString() });
+  const sig = crypto.createHmac("sha256", decryptWebhookSecret(secret)).update(body).digest("hex");
+
+  try {
+    // safeFetch resolves and pins the connection to a single validated IP
+    // (and re-validates + re-pins every redirect hop), so there's no
+    // separate re-resolution for a rebinding attack to exploit.
+    const res = await safeFetch(url, {
+      method: "POST",
+      headers: {
+        "Content-Type": "application/json",
+        "X-Epicure-Signature": `sha256=${sig}`,
+        "X-Epicure-Event": event,
+      },
+      body,
+      signal: AbortSignal.timeout(10000),
+    });
+    return { statusCode: res.status, success: res.ok };
+  } catch {
+    return { statusCode: 0, success: false };
+  }
+}