feat: integrate user preferences for online status in WebSocket gateway

- Added `UsersService` to manage user preferences in `EventsGateway`.
- Enhanced online/offline broadcasting to respect user `showOnlineStatus` preference.
- Updated `handleTyping` and `check_status` to verify user preferences before emitting events.
- Abstracted status broadcasting logic into `broadcastStatus`.

backend/src/realtime/events.gateway.spec.ts

@@ -1,6 +1,7 @@
 import { ConfigService } from "@nestjs/config";
 import { Test, TestingModule } from "@nestjs/testing";
 import { JwtService } from "../crypto/services/jwt.service";
+import { UsersService } from "../users/users.service";
 import { EventsGateway } from "./events.gateway";
 
 describe("EventsGateway", () => {
@@ -15,12 +16,17 @@ describe("EventsGateway", () => {
 		get: jest.fn().mockReturnValue("secret-password-32-chars-long-!!!"),
 	};
 
+	const mockUsersService = {
+		findOne: jest.fn(),
+	};
+
 	beforeEach(async () => {
 		const module: TestingModule = await Test.createTestingModule({
 			providers: [
 				EventsGateway,
 				{ provide: JwtService, useValue: mockJwtService },
 				{ provide: ConfigService, useValue: mockConfigService },
+				{ provide: UsersService, useValue: mockUsersService },
 			],
 		}).compile();