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/pyasn1_modules/rfc6010.py

@@ -0,0 +1,88 @@
+#
+# This file is part of pyasn1-modules software.
+#
+# Created by Russ Housley with assistance from asn1ate v.0.6.0.
+# Modified by Russ Housley to add maps for use with opentypes.
+#
+# Copyright (c) 2019, Vigil Security, LLC
+# License: http://snmplabs.com/pyasn1/license.html
+#
+# Certificate Extension for CMS Content Constraints (CCC)
+#
+# ASN.1 source from:
+# https://www.rfc-editor.org/rfc/rfc6010.txt
+#
+
+from pyasn1.type import constraint
+from pyasn1.type import namedtype
+from pyasn1.type import namedval
+from pyasn1.type import univ
+
+from pyasn1_modules import rfc5280
+
+MAX = float('inf')
+
+
+AttributeType = rfc5280.AttributeType
+
+AttributeValue = rfc5280.AttributeValue
+
+
+id_ct_anyContentType = univ.ObjectIdentifier('1.2.840.113549.1.9.16.1.0')
+
+
+class AttrConstraint(univ.Sequence):
+    pass
+
+AttrConstraint.componentType = namedtype.NamedTypes(
+    namedtype.NamedType('attrType', AttributeType()),
+    namedtype.NamedType('attrValues', univ.SetOf(
+        componentType=AttributeValue()).subtype(subtypeSpec=constraint.ValueSizeConstraint(1, MAX)))
+)
+
+
+class AttrConstraintList(univ.SequenceOf):
+    pass
+
+AttrConstraintList.componentType = AttrConstraint()
+AttrConstraintList.subtypeSpec=constraint.ValueSizeConstraint(1, MAX)
+
+
+class ContentTypeGeneration(univ.Enumerated):
+    pass
+
+ContentTypeGeneration.namedValues = namedval.NamedValues(
+    ('canSource', 0),
+    ('cannotSource', 1)
+)
+
+
+class ContentTypeConstraint(univ.Sequence):
+    pass
+
+ContentTypeConstraint.componentType = namedtype.NamedTypes(
+    namedtype.NamedType('contentType', univ.ObjectIdentifier()),
+    namedtype.DefaultedNamedType('canSource', ContentTypeGeneration().subtype(value='canSource')),
+    namedtype.OptionalNamedType('attrConstraints', AttrConstraintList())
+)
+
+
+# CMS Content Constraints (CCC) Extension and Object Identifier
+
+id_pe_cmsContentConstraints = univ.ObjectIdentifier('1.3.6.1.5.5.7.1.18')
+
+class CMSContentConstraints(univ.SequenceOf):
+    pass
+
+CMSContentConstraints.componentType = ContentTypeConstraint()
+CMSContentConstraints.subtypeSpec=constraint.ValueSizeConstraint(1, MAX)
+
+
+# Map of Certificate Extension OIDs to Extensions
+# To be added to the ones that are in rfc5280.py
+
+_certificateExtensionsMap = {
+    id_pe_cmsContentConstraints: CMSContentConstraints(),
+}
+
+rfc5280.certificateExtensionsMap.update(_certificateExtensionsMap)