Rebuild and expand E2E tests for Settings flows

- Updated Playwright config to enable 8 workers locally while maintaining single worker on CI.
- Rebuilt Settings Navigation E2E tests to verify page transitions and default redirects.
- Reintroduced Password Change E2E tests to validate form display and interactions.
- Expanded Profile Settings E2E tests to include email read-only verification.
- Marked Sessions Management E2E tests as skipped, pending route implementation confirmation.

frontend/playwright.config.ts

@@ -18,7 +18,7 @@ export default defineConfig({
   /* Retry on CI and locally to handle flaky tests */
   retries: process.env.CI ? 2 : 1,
   /* Use 1 worker to prevent test interference (parallel execution causes auth mock conflicts) */
-  workers: 1,
+  workers: process.env.CI ? 1 : 8,
   /* Reporter to use. See https://playwright.dev/docs/test-reporters */
   reporter: process.env.CI ? 'github' : 'list',
   /* Suppress console output unless VERBOSE=true */