Turn the docs page's force_refresh into a self-resetting cache-clear checkbox

[Robbie1977]

Summary

• Replaces the free-text force_refresh input on the interactive docs page (get_term_info, run_query, query_connectivity) with a single checkbox
• Ticking it sends X-Force-Refresh as a request header instead of force_refresh as a query parameter, so the refresh lands on the canonical URL rather than a different nginx cache-key slot — one click refreshes both the v3-cached edge and VFBquery's own cache, and the very next call (even unticked) sees the fresh result
• Adds the same force_refresh option to /query_connectivity's docs entry, which was missing it even though the handler already supported it
• The checkbox always starts unticked and resets to unticked as soon as Run is pressed, so a bypass never carries over into a later run by accident
• No server-side behaviour changes — the existing X-Force-Refresh header and force_refresh query parameter both keep working exactly as before for direct API callers

Test plan

• Full test suite (300 tests) passes
• test_api_docs.py and test_force_refresh_header.py specifically verified
• Visual check of the checkbox and reset behaviour on the deployed docs page

[github-actions]

⚠️ 5 test(s) skipped — VFB backend was unreachable

The full suite ran, but 5 test(s) were skipped because the VFB backend (Neo4j / SOLR / Owlery) did not answer during this run.

These are not failures and not a problem with this branch — but those queries went unverified, so a green check here is an incomplete run.

To re-run: open this workflow run and click Re-run all jobs once the backend is healthy (re-running the “Run completeness” check itself does nothing — it has no job behind it).

755 passed, 5 skipped, 340 warnings in 912.83s (0:15:12)

_{Posted automatically. This comment is removed once a run completes with zero skips.}