Added ingestor.store() support in NV-Ingest

[smasurekar]

NV-Ingest .store() for citation assets; read via source_location

Citation images and structured assets are written by NV-Ingest ingestor.store() (MinIO) instead of the ingestor’s __put_content_to_minio path. The RAG server and VLM load them using source.source_location and MinioOperator.get_object() (plus object_key_from_storage_uri). Document summaries are unchanged (get_payload / thumbnail IDs).

Citation storage is not backward compatible: Citation media that was written to MinIO under unique-thumbnail object keys (JSON payloads) is no longer what the RAG server resolves at query time. NV-Ingest now persists assets through .store(), and the server loads them via source_location. Older vectors may still reference the thumbnail-based layout; re-ingesting aligns metadata and object paths so citation images resolve correctly.

Checklist

• I am familiar with the Contributing Guidelines.
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• New or existing tests cover these changes.
• The documentation is up to date with these changes.
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