Add preview streaming endpoint and update sample response handling

Commit notes

- Introduced a new API endpoint for streaming low-bitrate previews of published samples, enhancing user experience by allowing inline playback. - Updated sample response handling in various handlers to utilize the new preview proxy URL, ensuring consistent access to preview content across the application. - Refactored existing methods to replace presigned URLs with API-proxied URLs for previews, improving security and simplifying URL management.