feat(contracts): add notification.requested event schema (GOO-173)

Phase 1 RFC-004 prep — define the event contract that the notifications
module will publish through the Phase 0 outbox + Redis Streams backbone.

- Add notification.requested.schema.json (JSON Schema 2020-12) covering
  notificationId, userId, category, template, params, channels, locale,
  priority, dedupeKey, requestedAt
- Add NotificationRequestedPayload + supporting union types
  (NotificationCategory, NotificationChannel, NotificationLocale,
  NotificationPriority) to @goodgo/contracts-events barrel
- Register 'notification.requested' in KNOWN_EVENT_TYPES

Pure contract addition; no producer/consumer wiring yet (follow-up commits
in this branch will introduce the publisher refactor + BullMQ worker).

Co-Authored-By: Paperclip <noreply@paperclip.ing>

libs/contracts/events/src/event-types.ts

@@ -2,6 +2,7 @@ export const KNOWN_EVENT_TYPES = [
   'kyc.verified',
   'listing.approved',
   'payment.completed',
+  'notification.requested',
 ] as const;
 
 export type KnownEventType = (typeof KNOWN_EVENT_TYPES)[number];

libs/contracts/events/src/index.ts

@@ -35,3 +35,34 @@ export interface KycVerifiedPayload {
   verifiedAt: string;
   documentRefs: string[];
 }
+
+export type NotificationCategory =
+  | 'auth'
+  | 'kyc'
+  | 'listing'
+  | 'payment'
+  | 'subscription'
+  | 'inquiry'
+  | 'lead'
+  | 'agent'
+  | 'residential'
+  | 'system';
+
+export type NotificationChannel = 'email' | 'sms' | 'zalo' | 'fcm' | 'in_app';
+
+export type NotificationLocale = 'vi' | 'en';
+
+export type NotificationPriority = 'low' | 'normal' | 'high' | 'critical';
+
+export interface NotificationRequestedPayload {
+  notificationId: string;
+  userId: string;
+  category: NotificationCategory;
+  template: string;
+  params: Record<string, unknown>;
+  channels: NotificationChannel[];
+  locale?: NotificationLocale;
+  priority?: NotificationPriority;
+  dedupeKey?: string;
+  requestedAt: string;
+}