[configuration] Add image uploader for configuration logos

[Montekkundan]

Brief summary of changes

• Adds an image configuration type for study and login logos.
• Adds a configuration upload endpoint using the existing LORIS file upload handler.
• Validates uploaded file names, extensions, and image content.
• Lists valid images from htdocs/images in the configuration selectors.
• Adds a configurable upload directory and corresponding database patch.
• Updates the Raisinbread configuration data.
• Adds unit tests for image discovery, validation, and public paths.

Testing instructions

• Open http://localhost:8080/configuration/ as a user with the config permission.
• Confirm the study, login, and partner logo settings display image selectors.
• Upload a PNG, JPEG, GIF, or WebP image.
• Confirm the uploaded image appears in each image selector.
• Select the uploaded image, submit the form, and reload the page.
• Confirm the selected image remains saved and is publicly accessible.
• Attempt to upload a non-image file and confirm it is rejected.
• Add a Partner Logos field and confirm it starts with a blank selection.
• Run target=configuration npm run compile.

Link(s) to related issue(s)

• Resolves [configuration] Uploader #10812