Enhancement: Add progress tracking for large asset uploads

[leogdion]

Overview

Add progress reporting for asset uploads to improve UX during large file transfers.

Current API

// No progress feedback during upload
let data = try Data(contentsOf: largeVideoURL) // 200 MB
let result = try await service.uploadAssets(data: data)
// User waits with no feedback

Proposed API

// Option 1: Callback-based progress
let result = try await service.uploadAssets(
    data: data,
    progress: { bytesUploaded, totalBytes in
        let percent = Double(bytesUploaded) / Double(totalBytes) * 100
        print("Upload: \(percent)%")
    }
)

// Option 2: AsyncSequence of progress updates
for try await progress in service.uploadAssetsWithProgress(data: data) {
    switch progress {
    case .uploading(let bytes, let total):
        updateUI(bytes: bytes, total: total)
    case .completed(let result):
        handleResult(result)
    }
}

// Option 3: Publisher-based (Combine)
service.uploadAssetsPublisher(data: data)
    .sink(
        receiveValue: { progress in updateUI(progress) },
        receiveCompletion: { completion in handleCompletion(completion) }
    )

Benefits

• Better UX: Users see upload progress
• Timeout handling: Detect stalled uploads
• Cancellation support: Allow user to cancel long uploads
• Network diagnostics: Monitor upload speed

Implementation Notes

• Use URLSession's uploadTask(with:from:) progress monitoring
• Leverage OpenAPIRuntime's HTTPBody streaming
• Consider memory-efficient streaming for large files
• Add upload speed calculation (bytes/second)
• Support cancellation via Task cancellation

Considerations

• Which API style is most idiomatic for Swift Concurrency?
• Should progress be opt-in or always available?
• How to handle progress with batch uploads?
• Minimum file size threshold for progress tracking?

Related

• Implemented in Uploading Assets (assets/upload) #30 (uploadAssets)
• Consider combining with Enhancement: Support batch asset upload (multiple files) #201 (batch upload)