jpg-to-pdf and its six image-to-pdf-group siblings share the base tool's
registerImageToPdfRoute, which never registers into the toolRegistry the
generic /batch endpoint reads from. The shared conversion-preset settings
component routed any 2+-file submission to /batch regardless of tool, so
these presets 404'd with `Tool "<id>" not found` past the first file, while
the base image-to-pdf tool stayed unaffected because it bypasses that
dispatch entirely with its own settings component.
MULTI_FILE_TOOLS now includes every image-to-pdf-group preset, derived from
BASE_CONFIG instead of hardcoded, and the preset settings component checks
that set before choosing batch vs. a single combined request.
Fixes#627
