Expose QR code/Barcode content as text, metadata, or custom field in Paperless-ngx

Description Hello, First of all, thank you for your outstanding work on Paperless-ngx — I actively use it for document automation. I would like to propose a feature related to QR code (and barcode) handling during document consumption. Paperless-ngx correctly detects QR codes (via the BarcodePlugin / ZXING), and their content is visible in the logs (e.g., Barcode of type BarcodeFormat.QRCode found: SPC…). However, this information is not saved: • not in the OCR text, • not as metadata attached to the document, • not as a value in any custom field, • and not exposed via the REST API. This makes it impossible to reuse this valuable information in workflows, searches, tags, or automated post-consume scripts. I would suggest: Save detected QR code / barcode content as: • text inserted into the OCR output (for example, appended at the end), and/or • a specific metadata field (e.g., barcode_text or qr_code_content in the Docum…