* fix(upload): remove file type allowlist to support all file types
Removes the hardcoded MIME type allowlist from both frontend and backend
that was blocking uploads of file types like Word documents (.docx).
File size limit (10 MB) is still enforced. Content type detection is
preserved for metadata storage.
Closes MUL-123
* feat(upload): increase file size limit from 10 MB to 100 MB
Updates both frontend and backend to allow uploads up to 100 MB.