feat: granular per-category push notification settings

New Settings → Notifications section with a toggle per category (follow,
comment, reply, reaction, rating, mention, leftover-expiring, shared
shopping list) — previously it was all-or-nothing (browser permission only).

userNotificationPrefs (one row per user, defaults all-on so existing users
see no behavior change until they opt out of something). Gated the push
send in the three places that dispatch one: lib/notifications.ts (the 6
in-app notification types), the leftover-expiry cron, and shopping-list-notify
— in-app notification-center entries and email are unaffected, this only
gates the push itself, matching the literal ask.

Verified locally: GET/PUT round-trips correctly, disabling a category
and confirming the settings page renders all 8 toggles.

apps/web/lib/shopping-list-notify.ts

@@ -1,6 +1,7 @@
 import { db, shoppingLists, shoppingListMembers, eq } from "@epicure/db";
 import { sendPushNotification } from "@/lib/push";
 import { getMessages, formatMessage } from "@/lib/i18n/server";
+import { isNotificationCategoryEnabled } from "@/lib/notification-prefs";
 
 // formatMessage() is a plain {key} interpolator, not ICU-plural-aware, so
 // pluralization has to be resolved to a plain string before it's passed in.
@@ -53,6 +54,8 @@ export async function notifyShoppingListMembers(
 
   await Promise.all(
     recipients.map(async (recipient) => {
+      if (!(await isNotificationCategoryEnabled(recipient.id, "shoppingList"))) return;
+
       const messages = getMessages(recipient.locale);
       const title = messages.notifications.pushTitle.shoppingListUpdate;
       const body =