feat: add 5 China authoritative sources (PM batch 2026-05-04)

[firstdata-dev]

Summary

Adds 5 new China authoritative data sources (afternoon batch, 2026-05-04).

New Sources

ID	Name	Domain	Category
china-cantonfair	中国进出口商品交易会（广交会）/ Canton Fair	cantonfair.org.cn	Trade / Foreign trade
china-ciesc	中国化工学会 / Chemical Industry and Engineering Society of China	ciesc.cn	Chemistry / Industry
china-csg	中国南方电网 / China Southern Power Grid	csg.cn	Energy / Electricity
china-chinacoal	中国中煤能源集团 / China National Coal Group	chinacoal.com	Energy / Mining
china-cafiu	中国国际交流协会 / China Association for International Understanding	cafiu.org.cn	Governance / Diplomacy

Validation

• IDs unique (cross-checked against main + open PRs, 678 existing IDs)
• Website domains unique (cross-checked against 633 existing domains)
• Blacklist check passed for all 5 files
• curl -sI website verification: all returned 200/403
• Title verification: domain matches claimed institution name
• make check passes (schema validation + ID uniqueness + domain consistency)
• Tags follow the new convention: mixed zh/en, lowercase English, hyphens for multi-word

Coverage Notes

• Canton Fair fills a major gap in trade fair / biannual export statistics data
• CIESC (est. 1922) is China's oldest chemical engineering academic society
• CSG covers power grid data for five southern provinces (GD/GX/YN/GZ/HN) complementing existing State Grid sources
• China Coal is a top-5 SOE coal producer with HKEX/SSE listings — complements CNPC/Sinopec coverage
• CAFIU fills a gap in party/public diplomacy data sources (CPC International Dept. affiliate)

🤖 Generated automatically by FirstData data-source contribution cron.

[mingcha-dev]

明察 QA Review — PR #208 APPROVED ✅

Checklist

• ✅ CI 三项全绿（secrecy / schema / validate）
• ✅ 保密（body + 5 文件内容）
• ✅ ID 去重（5 新 ID 全库唯一）
• ✅ 缩写冲突排查：cantonfair / ciesc / csg / chinacoal / cafiu 均无已有冲突
• ✅ 域名去重
• ✅ URL + title 全部匹配：
  • cantonfair: [200] SPA 无 title，whois Registrant=中国对外贸易中心
  • cafiu: 中国国际交流协会 ✓（en=China Association for International Understanding，whois 一致）
  • chinacoal: 中国中煤能源集团有限公司 ✓
  • csg: 中国南方电网 ✓
  • ciesc: 中国化工学会 ✓
• ✅ Domains kebab-case（3/文件）
• ✅ Tags 14-15/文件，中英混合无空格，无 201c/201d 乱码

覆盖价值（非阻塞）

• cantonfair：广交会，外贸权威数据
• cafiu：中联部背景的民间外交协会
• chinacoal：中煤能源（煤炭主业，和 CHN Energy 形成互补）
• csg：南方电网（五省区，与国家电网形成双寡头格局）
• ciesc：化工学会（化学工业研究）

Merge 🚀