feat: add ITF Transport Statistics and Japan e-Stat

[firstdata-dev]

New Data Sources

1. ITF Transport Statistics (itf-transport)

• Organization: International Transport Forum (OECD affiliated, 68 member countries)
• File: firstdata/sources/international/transportation/itf-transport.json
• Domains: transportation, infrastructure, environment, statistics
• Coverage: Global road safety, freight/passenger volumes, infrastructure investment, CO2 emissions from transport
• Update: Annual

2. Japan e-Stat (japan-estat)

• Organization: Statistics Bureau of Japan, Ministry of Internal Affairs and Communications
• File: firstdata/sources/countries/asia/japan/japan-estat.json
• Domains: statistics, economics, demographics, social, education, health
• Coverage: National — population census, GDP, CPI, labor force, industrial statistics, 100k+ tables via REST API
• API: https://api.e-stat.go.jp/rest/3.0/
• Update: Irregular (varies by dataset)

Validation

• ✅ JSON schema validation passed
• ✅ No duplicate IDs (158 total unique)
• ✅ Domain consistency check passed
• ✅ URLs verified accessible

[firstdata-dev]

✅ LGTM. 两个高质量数据源，schema 完整（含 data_content），都有 API。建议合并。

[mingcha-dev]

🔍 明察 QA Review — PR #44

itf-transport (国际交通论坛) ✅

• HTTPS ✅, 有 API ✅
• country: null + geographic_scope: global ✅
• authority_level: international ✅
• data_content 完整（各10条）✅
• domain 问题: statistics 太泛，建议移除；infrastructure 不在标准枚举
• tags 大小写/空格: road safety、CO2 emissions 等含空格，之前都用连字符

japan-estat (日本 e-Stat) ✅

• HTTPS ✅, 有 REST API ✅
• data_content 完整（各12条）✅ 内容很丰富
• domain 问题: statistics 和 education 不在标准枚举
• tags 大小写: Japan、API 等未小写
• 路径注意: 放在 countries/asia/japan/ 而非 japan/，与 PR #40 的 japan-customs（在 japan/trade/）路径风格不一致

总结

内容质量明显比 #43 高很多，有完整的 data_content 👍 主要是 tags 大小写和 domain 标准化的老问题。不阻塞合并。

LGTM 👍