Implement multipart/form-data file upload support using busboy

[Robert0303-C]

Summary

This PR implements multipart/form-data file upload support using the busboy library.

Changes

• Add busboy and @types/busboy as dependencies in server package
• Implement multipart/form-data parsing with proper security limits:
  • MAX_FILE_SIZE: 100MB per file
  • MAX_FILES: 10 files max
  • MAX_FIELDS: 100 fields max
  • MAX_TOTAL_PARTS: 1000 parts max
  • MAX_HEADER_PAIRS: 2000 header pairs max
• Make collectParamsFromRequest async to support await for Promise-based parsing
• Extract fields and files from multipart body and pass to convertAndAddParams
• Files are stored as UploadFile objects with createReadStream method
• Handle multiple values for same field name
• Proper error handling with CommunicationError wrapper

Security

The implementation includes multiple security limits to prevent DoS attacks:

• File size limits per file
• Maximum number of files
• Maximum number of fields
• Maximum number of total parts
• Maximum number of header pairs

Notes

• The previous implementation threw a CommunicationError with message "multipart/form-data file uploads not yet implemented"
• The UploadFile type follows the existing interface from restfuncs-common with createReadStream

Fixes #6

[Robert0303-C]

/claim #6

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