Fix duplicate dependency constraint causing 500 errors

- Deduplicate dependencies by package name before inserting
- Some packages (like anyio) list the same dep (trio) multiple times with
  different version constraints for different extras
- The unique constraint on (artifact_id, project, package) rejected these
- Also removed debug logging from dependencies.py

backend/app/pypi_proxy.py

@@ -737,8 +737,16 @@ async def pypi_download_file(
         # Extract and store dependencies
         dependencies = _extract_dependencies(content, filename)
         if dependencies:
-            logger.info(f"PyPI proxy: extracted {len(dependencies)} dependencies from {filename}")
+            # Deduplicate dependencies by package name (keep first occurrence)
+            seen_packages = set()
+            unique_deps = []
             for dep_name, dep_version in dependencies:
+                if dep_name not in seen_packages:
+                    seen_packages.add(dep_name)
+                    unique_deps.append((dep_name, dep_version))
+
+            logger.info(f"PyPI proxy: extracted {len(unique_deps)} dependencies from {filename} (deduped from {len(dependencies)})")
+            for dep_name, dep_version in unique_deps:
                 # Check if this dependency already exists for this artifact
                 existing_dep = db.query(ArtifactDependency).filter(
                     ArtifactDependency.artifact_id == sha256,