Prevents silent no-op when user clicks submit before lq__exhibit_obj is ready
(exhibit not yet written to Dexie). Button now shows 'Loading...' spinner while
the exhibit record is resolving, eliminating the two-tap workaround needed on
first page load.
Also adds 7 Playwright tests for licensed user sign-in (leads_licensed_signin.test.ts)
covering success path, wrong credentials, email/identity tagging on captured leads,
identity isolation between staff members, and returning-session bypass.
Helpers: attach_leads_routes/setup_leads_test_page now accept exhibit_overrides
(e.g. license_li_json) to inject licensed users into mocked API responses.
seed_leads_loc import added to leads_auth.test.ts multi-exhibit test.
Total leads test coverage: 29 tests.
Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>
