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/jose/jwk.py

@@ -0,0 +1,79 @@
+from jose.backends.base import Key
+from jose.constants import ALGORITHMS
+from jose.exceptions import JWKError
+
+try:
+    from jose.backends import RSAKey  # noqa: F401
+except ImportError:
+    pass
+
+try:
+    from jose.backends import ECKey  # noqa: F401
+except ImportError:
+    pass
+
+try:
+    from jose.backends import AESKey  # noqa: F401
+except ImportError:
+    pass
+
+try:
+    from jose.backends import DIRKey  # noqa: F401
+except ImportError:
+    pass
+
+try:
+    from jose.backends import HMACKey  # noqa: F401
+except ImportError:
+    pass
+
+
+def get_key(algorithm):
+    if algorithm in ALGORITHMS.KEYS:
+        return ALGORITHMS.KEYS[algorithm]
+    elif algorithm in ALGORITHMS.HMAC:  # noqa: F811
+        return HMACKey
+    elif algorithm in ALGORITHMS.RSA:
+        from jose.backends import RSAKey  # noqa: F811
+
+        return RSAKey
+    elif algorithm in ALGORITHMS.EC:
+        from jose.backends import ECKey  # noqa: F811
+
+        return ECKey
+    elif algorithm in ALGORITHMS.AES:
+        from jose.backends import AESKey  # noqa: F811
+
+        return AESKey
+    elif algorithm == ALGORITHMS.DIR:
+        from jose.backends import DIRKey  # noqa: F811
+
+        return DIRKey
+    return None
+
+
+def register_key(algorithm, key_class):
+    if not issubclass(key_class, Key):
+        raise TypeError("Key class is not a subclass of jwk.Key")
+    ALGORITHMS.KEYS[algorithm] = key_class
+    ALGORITHMS.SUPPORTED.add(algorithm)
+    return True
+
+
+def construct(key_data, algorithm=None):
+    """
+    Construct a Key object for the given algorithm with the given
+    key_data.
+    """
+
+    # Allow for pulling the algorithm off of the passed in jwk.
+    if not algorithm and isinstance(key_data, dict):
+        algorithm = key_data.get("alg", None)
+
+    if not algorithm:
+        raise JWKError("Unable to find an algorithm for key")
+
+    key_class = get_key(algorithm)
+    if not key_class:
+        raise JWKError("Unable to find an algorithm for key")
+    return key_class(key_data, algorithm)