feat(phase1): add image storage utilities

- Create backend/services/image_storage.py with 4 core functions:
  - sanitize_filename(): remove unsafe chars, limit to 255 chars, convert to lowercase
  - get_unique_filename(): handle collisions with UUID suffix (format: {name}_{uuid8}_{variant}.jpg)
  - ensure_image_directories(): create /images/ root and category subdirs on startup
  - save_image(): save bytes to /images/{category}/{filename}, returns relative path
- Create comprehensive test suite (22 tests) covering all functionality
- Integrate ensure_image_directories() into FastAPI startup event
- Directory structure: /images/{category}/{filename}
- Collision handling: auto-suffix with UUID if filename exists
- All tests passing, pathlib.Path for safe operations

venv/lib/python3.12/site-packages/cryptography/x509/oid.py

@@ -0,0 +1,37 @@
+# This file is dual licensed under the terms of the Apache License, Version
+# 2.0, and the BSD License. See the LICENSE file in the root of this repository
+# for complete details.
+
+from __future__ import annotations
+
+from cryptography.hazmat._oid import (
+    AttributeOID,
+    AuthorityInformationAccessOID,
+    CertificatePoliciesOID,
+    CRLEntryExtensionOID,
+    ExtendedKeyUsageOID,
+    ExtensionOID,
+    NameOID,
+    ObjectIdentifier,
+    OCSPExtensionOID,
+    OtherNameFormOID,
+    PublicKeyAlgorithmOID,
+    SignatureAlgorithmOID,
+    SubjectInformationAccessOID,
+)
+
+__all__ = [
+    "AttributeOID",
+    "AuthorityInformationAccessOID",
+    "CRLEntryExtensionOID",
+    "CertificatePoliciesOID",
+    "ExtendedKeyUsageOID",
+    "ExtensionOID",
+    "NameOID",
+    "OCSPExtensionOID",
+    "ObjectIdentifier",
+    "OtherNameFormOID",
+    "PublicKeyAlgorithmOID",
+    "SignatureAlgorithmOID",
+    "SubjectInformationAccessOID",
+]