Add a Playwright test that confirms Extension Console activation via shared mod url

[mnholtz]

Create a Playwright test that effectively replaces the manual regression checklist test "Activate mod via URL when logged in and have the browser extension" under the "Extension Console Activation" test group: https://www.notion.so/pixiebrix/Release-Checklist-Template-6d435dbf9a464f119ac6202b05d9c3b5?pvs=4#3afe7c8fc2f84c70a6ab86a8b5c1bcc0

Acceptance Criteria

Add a Playwright test that:

• Visits a shared mod url, e.g. https://app.pixiebrix.com/activate?id=%40pixies%2Fhn%2Fsearch-quickback
• Asserts that the user is taken to the Extension Console activation page
• Asserts that the mod can be activated
• Verifies that the activated mod works in https://pbx.vercel.app/
• After merging, remove the test from the regression checklist notion template https://www.notion.so/pixiebrix/Release-Checklist-Template-6d435dbf9a464f119ac6202b05d9c3b5?pvs=4#3afe7c8fc2f84c70a6ab86a8b5c1bcc0