Remove unused imports

- routes.py: Remove unused re, hashlib, ArtifactResponse imports
- storage.py: Remove unused ABC, abstractmethod imports (using Protocol instead)

backend/app/routes.py

@@ -17,9 +17,7 @@ from sqlalchemy.orm import Session
 from sqlalchemy import or_, func, text
 from typing import List, Optional, Literal
 import math
-import re
 import io
-import hashlib
 
 from .database import get_db
 from .storage import (
@@ -53,7 +51,6 @@ from .schemas import (
     TagSummary,
     PACKAGE_FORMATS,
     PACKAGE_PLATFORMS,
-    ArtifactResponse,
     ArtifactDetailResponse,
     ArtifactTagInfo,
     PackageArtifactResponse,

backend/app/storage.py

@@ -1,6 +1,5 @@
 import hashlib
 import logging
-from abc import ABC, abstractmethod
 from typing import (
     BinaryIO,
     Tuple,