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/passlib/ext/__init__.py

@@ -0,0 +1 @@
+

venv/lib/python3.12/site-packages/passlib/ext/django/__init__.py

@@ -0,0 +1,6 @@
+"""passlib.ext.django.models -- monkeypatch django hashing framework
+
+this plugin monkeypatches django's hashing framework
+so that it uses a passlib context object, allowing handling of arbitrary
+hashes in Django databases.
+"""

venv/lib/python3.12/site-packages/passlib/ext/django/models.py

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+"""passlib.ext.django.models -- monkeypatch django hashing framework"""
+#=============================================================================
+# imports
+#=============================================================================
+# core
+# site
+# pkg
+from passlib.context import CryptContext
+from passlib.ext.django.utils import DjangoContextAdapter
+# local
+__all__ = ["password_context"]
+
+#=============================================================================
+# global attrs
+#=============================================================================
+
+#: adapter instance used to drive most of this
+adapter = DjangoContextAdapter()
+
+# the context object which this patches contrib.auth to use for password hashing.
+# configuration controlled by ``settings.PASSLIB_CONFIG``.
+password_context = adapter.context
+
+#: hook callers should use if context is changed
+context_changed = adapter.reset_hashers
+
+#=============================================================================
+# main code
+#=============================================================================
+
+# load config & install monkeypatch
+adapter.load_model()
+
+#=============================================================================
+# eof
+#=============================================================================