[docs]: Translation Updates and Stats Improvements

[gked]

Changes Made

1. Added Russian translations for API documentation:

   • Translated introduction.md, rpc.md, and other API docs to Russian
   • Maintained technical terms and code examples in their original form
   • Ensured proper formatting and structure in translations

2. Fixed file naming consistency:

   • Renamed Russian documentation files to include _ru suffix
   • Updated navigation configurations to reflect new file names
   • Preserved README.md as a special case without suffix

3. Improved translation statistics script:

   • Enhanced language detection for both path and filename suffixes
   • Reorganized output format with Coverage Matrix at the top
   • Added detailed missing translations section with file mapping
   • Added checklist format for tracking needed translations

4. Updated navigation structure:

   • Aligned Russian and English navigation configurations
   • Fixed relative paths in documentation references
   • Updated cross-documentation links to use correct paths

Current Translation Status

• Russian translation coverage: 89.5% (17/19 files)
• Only 2 files pending Russian translation:
  • dev/node/source.md
  • translation_stats.md
• Other languages (DE, FR, KO, ES, IT, ZH) pending translation

Testing Done

• Verified all Russian translations render correctly
• Confirmed navigation works in both English and Russian versions
• Tested translation statistics script functionality
• Validated all cross-documentation links