feat: restructure test infrastructure with unit/integration/system separation

Test Organization:
- Create tests/unit/, tests/integration/, tests/system/ directories
- Move existing tests into appropriate categories
- Add pytest markers (@pytest.mark.unit, @pytest.mark.integration)

Shared Fixtures:
- Create conftest.py with SQLite engine (for unit tests)
- Add PostgreSQL session fixture with transaction rollback
- Add TestClient fixture for API tests

Configuration:
- Update pyproject.toml with asyncio_mode=auto
- Add test markers and default addopts
- Add aiosqlite dependency for SQLite support

E2E Testing:
- Initialize Playwright in e2e/ directory
- Add playwright.config.ts
- Create login flow E2E test

Build:
- Add test-unit, test-integration, test-system, test-e2e to Makefile
- Update test target to run all categories
- Add testing documentation to README

Note: Some tests have import issues due to missing python-jose
package in dev environment. This needs to be addressed separately.

e2e/tests/login.spec.ts

@@ -0,0 +1,32 @@
+import { test, expect } from '@playwright/test';
+
+test.describe('Login Flow', () => {
+  test('login page is accessible', async ({ page }) => {
+    await page.goto('/login');
+    
+    // Verify login page content
+    await expect(page.getByText('Sign in required')).toBeVisible();
+    await expect(page.getByText('Continue to login')).toBeVisible();
+  });
+
+  test('redirects to home after login', async ({ page }) => {
+    await page.goto('/login');
+    
+    // Click login button
+    await page.getByText('Continue to login').click();
+    
+    // Should redirect to OAuth provider (this is a simplified check)
+    // In real tests, you'd mock the OAuth flow or use test credentials
+    await expect(page).toHaveURL(/.*authentik.*/);
+  });
+});
+
+test.describe('Protected Routes', () => {
+  test('redirects unauthenticated users to login', async ({ page }) => {
+    await page.goto('/projects');
+    
+    // Should be redirected to login page
+    await expect(page).toHaveURL(/.*login.*/);
+    await expect(page.getByText('Sign in required')).toBeVisible();
+  });
+});