trial-expired-popup fixture

The trial-expiry-upgrade e2e spec drives the real chrome-extension://<id>/popup.html and options.html#senders / #upgrade surfaces, so no html host page is actually required for the in-page assertions.

This file is shipped because the per-spec allowed_paths inventory in .lead/tasks/phase1-w4-t3.json lists it, and keeping the fixture as a documented placeholder avoids a follow-up "create empty file" task. The spec seeds an expired-trial chrome.storage.local.'mailshade.license' payload (trialEndsAt = now - 1 day, no licenseKey) before opening the popup; see docs/e2e-trial-expiry-upgrade.md for the harness contract.