Publish API contract documentation for v0.24.0

[weilun88313]

Summary

• Publish the Lensmor public API contract as v0.24.0 with 30 documented operations.
• Add POST /external/events/{id}/visitors/unlock and POST /external/events/{id}/full-access/unlock.
• Document visitor/full-access prechecks, dynamic 0–5000 credit usage, idempotency, access-layer prerequisites, and failure states.
• Add credit add-on balance fields and update personnel/contact sourceType from a nullable string to a normalized string array.
• Keep agent-only integrations, debug routes, and deprecated compatibility endpoints outside the public contract.

Production contract evidence

• Compared against production backend master at tag V1.0.3 (2f5db518).
• Confirmed both new controllers, current credit prices, access-state behavior, response fields, add-on balance fields, and normalized source labels in production code.
• Authenticated production probes confirmed credit balance, event listing, and both new precheck action types.
• Both new POST routes were probed with an impossible event ID and returned 404 EVENT_NOT_FOUND; no unlock was created and no credits were consumed.

Validation

• python3 scripts/test_sync_public_assets.py — 15 tests passed
• python3 scripts/sync-public-assets.py --check — generated assets current
• npx @redocly/cli@latest lint openapi.json — 0 errors, 0 warnings
• npx mintlify@latest validate --telemetry=false — passed in a clean tracked-content copy
• npx mintlify@latest broken-links --telemetry=false — no broken links
• Browser-checked the visitor unlock, full-access unlock, precheck, and unlock guide pages in local Mintlify preview
• Confirmed all three OpenAPI copies are byte-identical and expose exactly 30 public operations

Release state

The repository update is ready for review. The live documentation remains on v0.23.1 until this PR is reviewed and merged into main by the Lensmor team.

[weilun88313]

Superseded by #19 on the canonical docs/v024-production-contract branch so Mintlify can receive a fresh PR lifecycle.