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/verification.py

@@ -0,0 +1,34 @@
+# 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
+
+import typing
+
+from cryptography.hazmat.bindings._rust import x509 as rust_x509
+from cryptography.x509.general_name import DNSName, IPAddress
+
+__all__ = [
+    "ClientVerifier",
+    "Criticality",
+    "ExtensionPolicy",
+    "Policy",
+    "PolicyBuilder",
+    "ServerVerifier",
+    "Store",
+    "Subject",
+    "VerificationError",
+    "VerifiedClient",
+]
+
+Store = rust_x509.Store
+Subject = typing.Union[DNSName, IPAddress]
+VerifiedClient = rust_x509.VerifiedClient
+ClientVerifier = rust_x509.ClientVerifier
+ServerVerifier = rust_x509.ServerVerifier
+PolicyBuilder = rust_x509.PolicyBuilder
+Policy = rust_x509.Policy
+ExtensionPolicy = rust_x509.ExtensionPolicy
+Criticality = rust_x509.Criticality
+VerificationError = rust_x509.VerificationError