Start an asynchronous bulk upload of entries via CSV.

Validates the target application list and CSV structure up front, then enqueues a background job that validates the uploaded rows and, if valid, automatically inserts all rows in a single transaction. If row validation or commit fails, the entire transaction is rolled back and the job ends in FAILED. Row-validation failures provide actionable input feedback; unexpected processing failures return only a generic message and the job reference to quote to support. There is a file size limitation of 5MB.