18504 - Add TUS resumable upload entity

[ghultink]

Summary

Adds $sdk->tus entity for TUS protocol resumable uploads via /sapi/tus.

Methods

Method	HTTP	Endpoint	Description
initUpload()	POST	/sapi/tus	Create upload, returns uploadId + presigned S3 URLs
getStatus()	HEAD	/sapi/tus/{id}	Get offset + remaining presigned URLs (resume)
complete()	POST	/sapi/tus/{id}/complete	Finalize S3 multipart upload
abort()	DELETE	/sapi/tus/{id}	Terminate upload, clean up S3
signPart()	GET	/sapi/tus/{id}/sign/{part}	Get fresh presigned URL for a part

Usage

$sdk = Sdk::withRPCTokenAuthentication($pub, $id, $secret);

// 1. Init upload
$response = $sdk->tus->initUpload('video.mp4', 104857600);
$body = $response->getDecodedBody();
// $body contains uploadId, presignedUrls, partSize

// 2. Client uploads parts directly to S3 via presigned URLs

// 3. Complete
$sdk->tus->complete($body['uploadId'], $completedParts);

Design

• File data never passes through PHP — only TUS coordination via SAPI
• Same mechanism as OVP6 and Uppy companion use
• Follows SDK entity pattern with async-first + AutoAsyncToSyncCaller