docs(api): document integration management endpoints

[alick-liming]

Summary

• document the nine public /integration/* APIs in Chinese and English
• add request, response, permission, rate-limit, audit, masking, and key-rotation behavior from the latest fc-datasource main branch
• update the On-call and consolidated OpenAPI specs, Mintlify navigation, and API catalogs

Validation

• python3 scripts/lint_openapi.py — 12 spec files, no violations
• bilingual path, response, navigation, and catalog parity checks
• semantic scope check confirmed no pre-existing OpenAPI object changed
• git diff --check

Scope / Notes

• keeps the existing /datasource/* API documentation unchanged
• real HTTP examples were not captured because no development APP Key was available; examples were generated from the current backend contracts
• mint broken-links could not complete because the Mint CLI is not installed locally and npx initialization stalled