Live-site canary: detect geocaching.com contract drift before users do

[rfsbraz]

Description

The e2e suite runs against a mocked geocache page and mocked logbook API, so CI stays green forever even when the real site changes and breaks the extension - which is exactly how the breakage in #85 shipped unnoticed. A real-page Playwright suite already exists for this, but tests/e2e/fixtures/real-pages/ is empty, so it silently skips.

The extension's contract with geocaching.com is narrow and assertable: page jQuery ($), userToken, the tmplCacheLogRow template, #cache_logs_table/#cache_logs_container, and the /seek/geocache.logbook endpoint's pageInfo.rows/data response shape.

Proposed Fix

• Capture a real cache page into tests/e2e/fixtures/real-pages/ so the existing suite actually runs (also directly unblocks reproducing [Bug] Extension not working #85)
• Add a scheduled (weekly + manual) CI job that fetches a live public cache page and probes the logbook endpoint, asserting each contract point above; failure = an issue-worthy alert instead of a user report
• Refresh the fixture periodically so it tracks the live site