Implement comprehensive frontend integration testing with Playwright

- Add Playwright E2E testing framework with cross-browser support (Chrome, Firefox)
- Create authentication helpers for CalDAV server integration
- Implement calendar interaction helpers with event creation, drag-and-drop, and view switching
- Add comprehensive drag-and-drop test suite with event cleanup
- Configure CI/CD integration with Gitea Actions for headless testing
- Support both local development and CI environments with proper dependency management
- Include video recording, screenshots, and HTML reporting for test debugging
- Handle Firefox-specific timing and interaction challenges with force clicks and timeouts

🤖 Generated with [Claude Code](https://claude.ai/code)

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

frontend/e2e/helpers/auth-helpers.ts

@@ -0,0 +1,63 @@
+import { Page, expect } from '@playwright/test';
+
+export class AuthHelpers {
+  constructor(private page: Page) {}
+
+  async loginWithTestCredentials() {
+    await this.page.goto('/login');
+    
+    // Use environment variables for test credentials
+    const serverUrl = process.env.TEST_CALDAV_SERVER || 'https://baikal.rcjohnstone.com/dav.php/';
+    const username = process.env.TEST_CALDAV_USERNAME || 'test';
+    const password = process.env.TEST_CALDAV_PASSWORD || 'I0W?7`|Cs6tA`s';
+    
+    await this.page.getByLabel('CalDAV Server URL').fill(serverUrl);
+    await this.page.getByRole('textbox', { name: 'Username' }).fill(username);
+    await this.page.getByLabel('Password').fill(password);
+    
+    await this.page.getByRole('button', { name: 'Sign In' }).click();
+    
+    // Wait for login to complete - either success (redirect) or error message
+    await Promise.race([
+      this.page.waitForURL(/.*\/calendar/, { timeout: 10000 }),
+      this.page.locator('.error-message').waitFor({ state: 'visible', timeout: 10000 })
+    ]);
+    
+    // If we're on the calendar page, verify the interface loaded
+    if (this.page.url().includes('/calendar') || (!this.page.url().includes('/login'))) {
+      await expect(this.page.locator('.calendar-grid').or(this.page.locator('.sidebar'))).toBeVisible({ timeout: 5000 });
+    }
+  }
+
+  async logout() {
+    // Look for logout button in sidebar - it might be text or button
+    const logoutButton = this.page.locator('text=Logout').or(this.page.getByRole('button', { name: 'Logout' }));
+    await logoutButton.click();
+    
+    // Should redirect to login page
+    await expect(this.page).toHaveURL(/.*\/login/);
+  }
+
+  async isLoggedIn(): Promise<boolean> {
+    try {
+      // Check if we're on the calendar page
+      const currentUrl = this.page.url();
+      if (!currentUrl.includes('/calendar') && !currentUrl.includes('/') || currentUrl.includes('/login')) {
+        return false;
+      }
+      
+      // Look for calendar interface elements instead of user-info
+      await expect(this.page.locator('.calendar-grid').or(this.page.locator('.sidebar'))).toBeVisible({ timeout: 5000 });
+      return true;
+    } catch {
+      return false;
+    }
+  }
+
+  async ensureLoggedIn() {
+    const loggedIn = await this.isLoggedIn();
+    if (!loggedIn) {
+      await this.loginWithTestCredentials();
+    }
+  }
+}