Get file detail (admin)
Returns a single remittance or return file scoped to the resolved institution (the id resolves the remittance table first, then the return table). Its content is the base64-encoded decrypted body only when the caller is authorized for cleartext access; otherwise the content is elided. A file belonging to another institution returns 404.
Path Parameters
Remittance or return file id (UUID)
Response
OK
Content is the base64-encoded decrypted file body, returned ONLY when the caller is authorized for cleartext access (all PII classes revealed); otherwise it is elided — the field is OMITTED entirely (omitempty), never partially redacted and never an empty placeholder.

