Storage backends load their native drivers

Alternative storage backends ship as modules beside the portal rather than inside it. Their native libraries — the pieces that are not .NET code — were being removed when the image was assembled, because nothing could load them from a module folder anyway. That left Snowflake and Cosmos looking installable while a deployment that actually selected one would have failed the moment it called into the driver.

Modules can now carry native libraries, and the portal finds them at the moment they are needed, picking the build that matches the machine it is running on. Nothing changes for a deployment on PostgreSQL, which is every memex portal today; what changes is that the other backends are now genuinely shippable.

This also removes the last blocker on moving image-only features — such as social share-card rendering, which needs a graphics library — out of the base image and into optional modules.