[Feature Request] Flexible File Extension Handling for Consumer

Description Summary Allow users to configure whether the paperless-ngx consumer should accept files without extensions or enforce strict extension checking, to maintain backward compatibility while enabling more flexible file consumption. Problem Description Currently, when a file without an extension is placed in the consumer directory (e.g., a PDF named "2020-Drivers license"), the system fails to process these files completely. The warning message shows: This behavior differs from the web interface upload method, which successfully processes files without extensions. There is #11974 with more chat/info. Use Case Some users might have files without extensions that are still valid documents (e.g., PDFs created by certain applications or scanned documents) and want to be able to process them automatically via the consumer directory. Other Proposed Solution Add a new setting in the configuration that allows users to: 1. Maintain the curr…