feat: Add comprehensive testing infrastructure

Implements robust testing setup with Playwright global auth, reusable test
helpers, Docker support, and CI/CD integration with Gitea Actions.

## Changes

### Playwright Setup
- Add global auth setup with storage state reuse (tests/playwright/auth.setup.ts)
- Fix auth setup to clear existing state before fresh login
- Create reusable performOAuthLogin helper (tests/playwright/helpers.ts)
- Configure dotenv loading for environment variables in playwright.config.ts

### Magnitude Configuration
- Update to use Claude Sonnet 4.5 (claude-sonnet-4-5-20250514)
- Create reusable loginFlow helper (tests/magnitude/helpers.ts)
- Fix smoke test to check login page instead of non-existent homepage

### Docker Support
- Add Dockerfile.playwright with non-root user (pwuser) for security
- Uses official Playwright Docker image (mcr.microsoft.com/playwright:v1.49.1-noble)
- Provides consistent testing environment across users and CI/CD

### CI/CD Integration
- Add Gitea Actions workflow (.gitea/workflows/magnitude.yml)
- Runs Magnitude tests on every push and PR
- Starts SurrealDB and Next.js dev server automatically
- Uploads test results as artifacts (30-day retention)

### Documentation
- Add comprehensive testing setup docs to AGENTS.md:
  - Playwright Docker setup instructions
  - CI/CD with Gitea Actions
  - Testing framework separation (Playwright vs Magnitude)
  - Required secrets for CI/CD

### Testing Best Practices
- Separate Playwright (manual + global auth) from Magnitude (automated E2E)
- Reusable helpers reduce code duplication
- Both frameworks work independently

## Testing

- ✅ Playwright auth setup test passes (5.6s)
- ✅ Magnitude smoke test passes
- ✅ OAuth flow works correctly with helper function

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

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

tests/playwright/helpers.ts

@@ -0,0 +1,78 @@
+/**
+ * Reusable test helpers for Playwright tests
+ *
+ * These helpers encapsulate common test patterns to reduce code duplication
+ * and make tests more maintainable.
+ */
+
+import { Page, expect } from '@playwright/test';
+
+const TEST_HANDLE = process.env.TEST_BLUESKY_HANDLE;
+const TEST_PASSWORD = process.env.TEST_BLUESKY_PASSWORD;
+
+if (!TEST_HANDLE || !TEST_PASSWORD) {
+  throw new Error(
+    'TEST_BLUESKY_HANDLE and TEST_BLUESKY_PASSWORD must be set in .env file'
+  );
+}
+
+/**
+ * Performs complete OAuth login flow
+ *
+ * This function navigates to the login page and completes the full OAuth flow:
+ * 1. Navigate to /login
+ * 2. Enter handle and click "Log in with Bluesky"
+ * 3. Wait for redirect to Bluesky OAuth page
+ * 4. Enter password and click "Sign in"
+ * 5. Click "Authorize" button
+ * 6. Wait for redirect to /chat
+ * 7. Verify authentication successful
+ *
+ * @param page - The Playwright Page object
+ */
+export async function performOAuthLogin(page: Page) {
+  console.log('[Helper] Starting OAuth login flow');
+
+  // Navigate to login page
+  await page.goto('/login');
+
+  // Fill in handle and initiate OAuth
+  await page.getByLabel('Your Handle').fill(TEST_HANDLE!);
+
+  // Click button and wait for navigation to Bluesky OAuth page
+  await Promise.all([
+    page.waitForURL('**/bsky.social/**', { timeout: 30000 }),
+    page.getByRole('button', { name: 'Log in with Bluesky' }).click(),
+  ]);
+  console.log('[Helper] Redirected to Bluesky OAuth page');
+
+  // The identifier is pre-filled from our login flow, just fill in password
+  // Use getByRole to avoid strict mode violations with multiple "Password" labeled elements
+  await page.getByRole('textbox', { name: 'Password' }).fill(TEST_PASSWORD!);
+
+  // Click Sign in button
+  await page.getByRole('button', { name: /sign in/i }).click();
+
+  // Wait for the OAuth authorization page by looking for the Authorize button
+  await page.getByRole('button', { name: 'Authorize' }).waitFor({ timeout: 10000 });
+  console.log('[Helper] On OAuth authorization page');
+
+  // Click Authorize button to grant access and wait for redirect
+  await Promise.all([
+    page.waitForURL('**/chat', { timeout: 20000 }),
+    page.getByRole('button', { name: 'Authorize' }).click(),
+  ]);
+  console.log('[Helper] Successfully authorized, redirected to /chat');
+
+  // Verify we're actually logged in by checking for Profile nav link
+  await expect(page.getByText('Profile')).toBeVisible({ timeout: 5000 });
+  console.log('[Helper] Verified authentication successful');
+}
+
+/**
+ * Test credentials for use in tests that need them directly
+ */
+export const TEST_CREDENTIALS = {
+  handle: TEST_HANDLE,
+  password: TEST_PASSWORD,
+} as const;