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/ldap3/operation/unbind.py

@@ -0,0 +1,32 @@
+"""
+"""
+
+# Created on 2013.09.03
+#
+# Author: Giovanni Cannata
+#
+# Copyright 2013 - 2020 Giovanni Cannata
+#
+# This file is part of ldap3.
+#
+# ldap3 is free software: you can redistribute it and/or modify
+# it under the terms of the GNU Lesser General Public License as published
+# by the Free Software Foundation, either version 3 of the License, or
+# (at your option) any later version.
+#
+# ldap3 is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU Lesser General Public License for more details.
+#
+# You should have received a copy of the GNU Lesser General Public License
+# along with ldap3 in the COPYING and COPYING.LESSER files.
+# If not, see <http://www.gnu.org/licenses/>.
+
+from ..protocol.rfc4511 import UnbindRequest
+
+
+def unbind_operation():
+    # UnbindRequest ::= [APPLICATION 2] NULL
+    request = UnbindRequest()
+    return request