Updated Content-Disposition header generation to use mime.FormatMediaType
from the standard library, which properly handles non-ASCII characters
and special characters per RFC 6266.
Changes:
- weed/server/common.go: Updated adjustHeaderContentDisposition to use
mime.FormatMediaType instead of manual escaping with fileNameEscaper
- weed/operation/upload_content.go: Updated multipart form Content-Disposition
to use mime.FormatMediaType
- weed/server/volume_server_handlers_read.go: Removed unused fileNameEscaper
This ensures correct filename display for international users across
filer downloads and file uploads.
Fixes#7634