Refactor the admin storage backend creation and editing flows to use
provider-specific pages (e.g., `/admin/storage/new/sftp`) instead of a
single generic form. This ensures only relevant fields are rendered for
each storage provider (such as SFTP, S3, or WebDAV).
Additionally:
- Prevent mutation of the storage provider type during backend edits.
- Add comprehensive unit tests for provider-specific rendering, edit
validation, and CSRF/admin route protection.
- Introduce S3-compatible storage backend support using minio-go.
- Add configuration options for local storage limits, box limits, and rate limiting.
- Implement storage backend selection (local vs S3) for anonymous and registered users.
- Add an `/admin/storage` management interface.
- Update documentation and environment examples with the new configuration variables.
- Add environment variables to configure anonymous uploads, daily upload caps, and default user storage limits.
- Update config loader to parse and validate the new settings.
- Implement backend logic to track daily usage and active storage per user.
- Update README and `.env.example` to document the new settings and admin panels.
- Add an API documentation page with curl and ShareX examples.
- Implement a dynamic ShareX configuration endpoint (`/api/v1/sharex/warpbox-anonymous.sxcu`) that generates a `.sxcu` file pre-configured with the instance's base URL.
- Update anonymous uploads to return a private management link (`manageUrl`) and a deletion link (`deleteUrl`) in JSON responses.
- Update README with details on Stage 3 Anonymous Integrations.
- Add styling for the new API documentation view and management details.
