docs: align attendee sources and add Simplified Chinese

[weilun88313]

Summary

• map product attendee labels to the public API sourceType values and document multi-source behavior
• add attendee-intelligence use cases and clarify separate base event and Visitor access semantics
• add Simplified Chinese core onboarding, attendee, access, and contact-unlock documentation
• update OpenAPI examples, machine-readable assets, SEO metadata, README, and changelog to v0.24.1

Production contract evidence

• sourceType is an array containing exhibitor, social, and/or visitors
• event personnel labels are event-scoped; profile and contact search can aggregate labels across related events
• Visitor is a separate access layer and availability is checked through action precheck
• no public source filter or hasVisitors event field is claimed

Validation

• python3 -m unittest scripts/test_sync_public_assets.py (16 passed)
• python3 scripts/sync-public-assets.py --check
• JSON validation and byte-identical OpenAPI copies
• Redocly 2.39.0 lint: 0 errors, 0 warnings
• npx --yes mintlify@latest validate
• local Mintlify browser QA for English/Chinese language switching, source taxonomy, attendee guide, and Personnel API Reference
• selected English, Chinese, and API Reference routes returned HTTP 200
• git diff --check