feat: implement ERP authentication service

Implement ErpAuthService with TDD approach:
- Add login(), close(), getSession(), isActive() methods
- Use Playwright chromium with headless:false for debugging
- Manage browser lifecycle and session state
- Handle authentication flow with ERP_LOCATORS
- Add integration tests for login scenarios
- Add unit tests for session management
- Fix dotenv config path in test setup

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

src/main/services/erp/erp-auth.ts

@@ -0,0 +1,93 @@
+import { chromium, type Browser, type BrowserContext, type Page } from 'playwright';
+import { ERP_LOCATORS } from './locators';
+import type { ErpConfig, ErpSession } from '../../types/erp.types';
+
+/**
+ * ERP Authentication Service
+ * Manages login session and browser lifecycle
+ */
+export class ErpAuthService {
+  private config: ErpConfig;
+  private session: ErpSession | null = null;
+
+  constructor(config: ErpConfig) {
+    this.config = config;
+  }
+
+  /**
+   * Login to ERP system and establish session
+   */
+  async login(): Promise<ErpSession> {
+    if (this.session?.isLoggedIn) {
+      return this.session;
+    }
+
+    // Launch browser
+    const browser = await chromium.launch({
+      headless: false, // Set to true for production
+      slowMo: 100, // Slow down for debugging
+    });
+
+    const context = await browser.newContext({
+      acceptDownloads: true,
+      viewport: { width: 1920, height: 1080 },
+    });
+
+    const page = await context.newPage();
+
+    // Navigate to login page
+    await page.goto(this.config.url);
+
+    // Wait for login form
+    await page.waitForSelector(ERP_LOCATORS.login.usernameInput);
+
+    // Fill credentials
+    await page.fill(ERP_LOCATORS.login.usernameInput, this.config.username);
+    await page.fill(ERP_LOCATORS.login.passwordInput, this.config.password);
+
+    // Submit login
+    await page.click(ERP_LOCATORS.login.submitButton);
+
+    // Wait for main page to load
+    await page.waitForURL(`${this.config.url}/**`);
+    await page.waitForSelector(ERP_LOCATORS.main.mainIframe, { timeout: 10000 });
+
+    // Create session
+    this.session = {
+      browser,
+      context,
+      page,
+      isLoggedIn: true,
+    };
+
+    return this.session;
+  }
+
+  /**
+   * Close browser and cleanup session
+   */
+  async close(): Promise<void> {
+    if (this.session) {
+      await this.session.context.close();
+      await this.session.browser.close();
+      this.session = null;
+    }
+  }
+
+  /**
+   * Get current session (must be logged in first)
+   */
+  getSession(): ErpSession {
+    if (!this.session?.isLoggedIn) {
+      throw new Error('Not logged in. Call login() first.');
+    }
+    return this.session;
+  }
+
+  /**
+   * Check if session is active
+   */
+  isActive(): boolean {
+    return this.session?.isLoggedIn ?? false;
+  }
+}