feat: implement authentication service

Add auth service that wraps Playwright service for user authentication.
Includes login/logout functionality and session management.

Co-Authored-By: Claude Sonnet 4.5 <noreply@anthropic.com>

src/main/models/auth.types.ts

@@ -0,0 +1,10 @@
+export interface AuthResult {
+  success: boolean;
+  message?: string;
+}
+
+export interface SessionInfo {
+  username: string;
+  isLoggedIn: boolean;
+  loginTime: Date;
+}

src/main/services/auth.service.ts

@@ -0,0 +1,54 @@
+import { PlaywrightService } from './playwright.service';
+import { Credentials, LoginResult } from '../models/playwright.types';
+import { AuthResult, SessionInfo } from '../models/auth.types';
+import { LoggerService } from './logger.service';
+
+export class AuthService {
+  private currentSession?: LoginResult;
+  private sessionInfo?: SessionInfo;
+
+  constructor(private playwrightService: PlaywrightService) {}
+
+  async login(credentials: Credentials): Promise<AuthResult> {
+    try {
+      LoggerService.info(`Logging in user: ${credentials.username}`);
+
+      const session = await this.playwrightService.login(credentials);
+      this.currentSession = session;
+      this.sessionInfo = {
+        username: credentials.username,
+        isLoggedIn: true,
+        loginTime: new Date(),
+      };
+
+      LoggerService.info('Login successful');
+      return { success: true, message: 'Login successful' };
+    } catch (error) {
+      LoggerService.error('Login failed', error);
+      return {
+        success: false,
+        message: error instanceof Error ? error.message : 'Unknown error',
+      };
+    }
+  }
+
+  async logout(): Promise<void> {
+    if (this.currentSession) {
+      LoggerService.info('Logging out...');
+
+      await this.playwrightService.closeBrowser();
+      this.currentSession = undefined;
+      this.sessionInfo = undefined;
+
+      LoggerService.info('Logout successful');
+    }
+  }
+
+  getSessionInfo(): SessionInfo | undefined {
+    return this.sessionInfo;
+  }
+
+  isLoggedIn(): boolean {
+    return this.sessionInfo?.isLoggedIn ?? false;
+  }
+}