WIP: Add E2E Contacts test to run on desktop and mobile in BrowserStack

[rwood-moz]

What Changed

Added new Contacts E2E tests to run in BrowserStack on both desktop and android.

• Added four BrowserStack Contacts tests: create/edit contact, delete contact, create/edit address book, and delete address book
• Added ContactsPage for locators, UI actions, assertions, cleanup, and Android navigation
• Added JMAP prefix cleanup
• Increased the Playwright global limit to 30 minutes, and staggered nightly starts by 45 minutes

Why

These tests cover contact and address-book behavior in the deployed Webmail app across desktop and Android BrowserStack projects. Unique test-data prefixes and cleanup help keep the shared account reusable.

Limitations and Notes

I worked with Codex AI to create this patch, reviewed the code and tested thoroughly.

• The Webmail auth for these new tests is the same as the other existing E2E tests (desktop auth saves/re-uses the browser auth context, mobile must sign in each test run)
• Runs using the shared test account must not overlap because setup sweeps the shared prefixes.
• TypeScript and Playwright test discovery passed; an independent read-only code review found no remaining actionable issues

Applicable Issues

Fixes #67.

QA Log

I ran the new Contacts E2E test against Webmail production on:

• Firefox desktop on my local machine
• The Playwright Android viewport on my local machine
• Firefox desktop in BrowserStack
• Chromium desktop in BrowserStack
• Safari desktop in BrowserStack
• Android Chrome in BrowserStack