feat: improve test setup and authentication handling

- Added `dev:test` script to package.json for streamlined testing without file watching.
- Introduced `kill-test-servers` script to ensure no existing servers are running on test ports before executing tests.
- Enhanced Playwright configuration to use mock agent for tests, ensuring consistent API responses and disabling rate limiting.
- Updated various test files to include authentication steps and handle login screens, improving reliability and reducing flakiness in tests.
- Added `global-setup` for e2e tests to ensure proper initialization before test execution.

apps/ui/tests/context/add-context-image.spec.ts

@@ -119,9 +119,6 @@ test.describe('Add Context Image', () => {
   test('should import an image file to context', async ({ page }) => {
     await setupProjectWithFixture(page, getFixturePath());
 
-    // Authenticate with the server before navigating
-    await authenticateForTests(page);
-
     await page.goto('/');
     await waitForNetworkIdle(page);