feat: Server-side presigned URL utilities for storage providers #2
Description
Description
Provide server-side helper functions that match the client-side storage plugins. When a user chooses S3, R2, or Azure on the client, they can import the corresponding server utility to generate presigned URLs without extra boilerplate.
Context
Currently users must write their own presigned URL generation logic. Since the module already knows about these providers on the client, offering matching server utilities reduces setup friction and keeps the client/server experience consistent.