Add large file upload enhancements and tests (#43)

- Add upload duration/throughput metrics (duration_ms, throughput_mbps) to response
- Add upload progress logging for large files (hash computation and multipart upload)
- Add client disconnect handling during uploads with proper cleanup
- Add upload progress tracking endpoint GET /upload/{upload_id}/progress
- Add large file upload tests (10MB, 100MB, 1GB)
- Add upload cancellation and timeout handling tests
- Add API documentation for upload endpoints with curl, Python, JavaScript examples

backend/app/schemas.py

@@ -412,6 +412,9 @@ class UploadResponse(BaseModel):
     content_type: Optional[str] = None
     original_name: Optional[str] = None
     created_at: Optional[datetime] = None
+    # Upload metrics (Issue #43)
+    duration_ms: Optional[int] = None  # Upload duration in milliseconds
+    throughput_mbps: Optional[float] = None  # Upload throughput in MB/s
 
 
 # Resumable upload schemas
@@ -478,6 +481,21 @@ class ResumableUploadStatusResponse(BaseModel):
     total_uploaded_bytes: int
 
 
+class UploadProgressResponse(BaseModel):
+    """Progress information for an in-flight upload"""
+
+    upload_id: str
+    status: str  # 'in_progress', 'completed', 'failed', 'not_found'
+    bytes_uploaded: int = 0
+    bytes_total: Optional[int] = None
+    percent_complete: Optional[float] = None
+    parts_uploaded: int = 0
+    parts_total: Optional[int] = None
+    started_at: Optional[datetime] = None
+    elapsed_seconds: Optional[float] = None
+    throughput_mbps: Optional[float] = None
+
+
 # Consumer schemas
 class ConsumerResponse(BaseModel):
     id: UUID