Remove with-bucket for record creation

[jma]

Context

All record classes inherit from SonarRecord (in sonar/modules/api.py), which
mixes in FilesMixin from invenio_records_files. This forces every record
creation to handle a with_bucket parameter, even for resources that never
attach files.

Improvement suggestion

Split SonarRecord into two classes:

• SonarRecord: base class without file support
• SonarRecordWithFiles(SonarRecord, FilesMixin): adds file/bucket support

Modules that need files: documents, deposits, organisations, collections
Modules that do not: users, subdivisions, projects

Acceptance criteria

• SonarRecord no longer inherits from FilesMixin
• File-capable modules use the new SonarRecordWithFiles
• No regressions in file upload/download for documents, deposits, etc.
• Tests pass