Refresh API contract documentation for v0.23.2

[weilun88313]

Summary

• publish the confirmed credit rule for company-name exhibitor search: non-empty results cost 50 credits and empty results cost 0
• align event, contact, unlock, and outreach schemas across OpenAPI, human documentation, and generated LLM assets
• keep /external/integrations/* excluded from the public API surface

Why

The public documentation had drifted from current backend behavior in billing, event metadata, contact response fields, and accepted-versus-success unlock submissions. This update restores contract parity and adds regression coverage for generated assets and endpoint-specific prose.

Impact

• bumps the documented contract to v0.23.2
• keeps the public surface at 28 operations
• documents sponsorMatchStarred, canonical event dataSource: "Lensmor", phone unlock billing, and typed LinkedIn outreach responses
• clarifies that unlock submissions may return either an asynchronous accepted task or an immediate no-work success result

Validation

• python3 -m unittest scripts/test_sync_public_assets.py — 14/14 passed
• python3 scripts/sync-public-assets.py --check — clean
• Redocly OpenAPI lint — 0 errors, 0 warnings
• git diff --check — clean
• specification review — 0 findings
• standards review — 0 findings