Implement backend upload/download API enhancements

- Add S3 multipart upload support for files > 100MB
- Add resumable upload API endpoints (init, upload part, complete, abort, status)
- Add HTTP range request support for partial downloads
- Add HEAD request endpoint for artifact metadata
- Add format-specific metadata extraction (deb, rpm, tar.gz, wheel, jar, zip)
- Add format_metadata column to artifacts table
- Add database migration for schema updates
- Add deduplication indicator in upload response
- Set Accept-Ranges header on downloads
- Return Content-Length header on all downloads

backend/app/schemas.py

@@ -1,5 +1,5 @@
 from datetime import datetime
-from typing import Optional, List
+from typing import Optional, List, Dict, Any
 from pydantic import BaseModel
 from uuid import UUID
 
@@ -51,6 +51,7 @@ class ArtifactResponse(BaseModel):
     created_at: datetime
     created_by: str
     ref_count: int
+    format_metadata: Optional[Dict[str, Any]] = None
 
     class Config:
         from_attributes = True
@@ -81,6 +82,53 @@ class UploadResponse(BaseModel):
     project: str
     package: str
     tag: Optional[str]
+    format_metadata: Optional[Dict[str, Any]] = None
+    deduplicated: bool = False
+
+
+# Resumable upload schemas
+class ResumableUploadInitRequest(BaseModel):
+    """Request to initiate a resumable upload"""
+    expected_hash: str  # SHA256 hash of the file (client must compute)
+    filename: str
+    content_type: Optional[str] = None
+    size: int
+    tag: Optional[str] = None
+
+
+class ResumableUploadInitResponse(BaseModel):
+    """Response from initiating a resumable upload"""
+    upload_id: Optional[str]  # None if file already exists
+    already_exists: bool
+    artifact_id: Optional[str] = None  # Set if already_exists is True
+    chunk_size: int  # Recommended chunk size for parts
+
+
+class ResumableUploadPartResponse(BaseModel):
+    """Response from uploading a part"""
+    part_number: int
+    etag: str
+
+
+class ResumableUploadCompleteRequest(BaseModel):
+    """Request to complete a resumable upload"""
+    tag: Optional[str] = None
+
+
+class ResumableUploadCompleteResponse(BaseModel):
+    """Response from completing a resumable upload"""
+    artifact_id: str
+    size: int
+    project: str
+    package: str
+    tag: Optional[str]
+
+
+class ResumableUploadStatusResponse(BaseModel):
+    """Status of a resumable upload"""
+    upload_id: str
+    uploaded_parts: List[int]
+    total_uploaded_bytes: int
 
 
 # Consumer schemas