feat: add China Ministry of Finance (MOF) data source

[firstdata-dev]

New Data Source: China Ministry of Finance (MOF)

ID: china-mof
Authority Level: government
Country: CN
Domains: finance, economics, government

Description

The Ministry of Finance of China is the primary fiscal authority responsible for government budgets, revenue/expenditure statistics, debt management, and taxation policy.

Data Coverage

• Monthly fiscal revenue and expenditure reports
• Annual government budget and settlement data
• Government debt statistics (central and local)
• Transfer payment data
• Government procurement statistics
• State-owned capital operation budget

Validation

• ✅ make check passed (all 157 IDs unique, schema valid, domains consistent)
• ✅ URLs verified accessible
• ✅ Bilingual (EN/ZH) metadata complete

Checklist

• data_url links to actual data page
• api_url is null (MOF has no public API)
• country is CN (national scope)
• domains uses lowercase
• tags include EN/ZH keywords
• ID unique in all-sources.json
• File path follows placement rules
• All URLs verified