feat(notifications): add multi-channel notification module with Email, FCM, templates, and event listeners

- Domain: NotificationLog/NotificationPreference entities, repositories, channel value object
- Infrastructure: EmailService (nodemailer/SMTP), FcmService (firebase-admin), TemplateService (Handlebars)
- Application: SendNotification CQRS command, UserRegistered + AgentVerified event listeners
- Presentation: NotificationsController with history, preferences, and templates endpoints
- Prisma: NotificationLog and NotificationPreference models with proper indexes
- Templates: Vietnamese notification templates for user.registered, agent.verified, listing.approved, inquiry.received, password.reset

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

apps/web/lib/api-client.ts

@@ -0,0 +1,56 @@
+const API_BASE_URL = process.env['NEXT_PUBLIC_API_URL'] || 'http://localhost:3001';
+
+export class ApiError extends Error {
+  constructor(
+    public status: number,
+    message: string,
+  ) {
+    super(message);
+    this.name = 'ApiError';
+  }
+}
+
+type RequestOptions = Omit<RequestInit, 'body'> & {
+  body?: unknown;
+};
+
+async function request<T>(endpoint: string, options: RequestOptions = {}): Promise<T> {
+  const { body, headers, ...rest } = options;
+
+  const res = await fetch(`${API_BASE_URL}${endpoint}`, {
+    ...rest,
+    headers: {
+      'Content-Type': 'application/json',
+      ...headers,
+    },
+    body: body ? JSON.stringify(body) : undefined,
+  });
+
+  if (!res.ok) {
+    const error = await res.json().catch(() => ({ message: res.statusText }));
+    throw new ApiError(res.status, error.message || 'Request failed');
+  }
+
+  return res.json();
+}
+
+function authHeaders(token: string): HeadersInit {
+  return { Authorization: `Bearer ${token}` };
+}
+
+export const apiClient = {
+  get: <T>(endpoint: string, headers?: HeadersInit) =>
+    request<T>(endpoint, { method: 'GET', headers }),
+
+  post: <T>(endpoint: string, body?: unknown, headers?: HeadersInit) =>
+    request<T>(endpoint, { method: 'POST', body, headers }),
+
+  patch: <T>(endpoint: string, body?: unknown, headers?: HeadersInit) =>
+    request<T>(endpoint, { method: 'PATCH', body, headers }),
+
+  authGet: <T>(endpoint: string, token: string) =>
+    request<T>(endpoint, { method: 'GET', headers: authHeaders(token) }),
+
+  authPost: <T>(endpoint: string, token: string, body?: unknown) =>
+    request<T>(endpoint, { method: 'POST', body, headers: authHeaders(token) }),
+};