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/pygments/styles/vs.py

@@ -0,0 +1,41 @@
+"""
+    pygments.styles.vs
+    ~~~~~~~~~~~~~~~~~~
+
+    Simple style with MS Visual Studio colors.
+
+    :copyright: Copyright 2006-present by the Pygments team, see AUTHORS.
+    :license: BSD, see LICENSE for details.
+"""
+
+from pygments.style import Style
+from pygments.token import Keyword, Name, Comment, String, Error, \
+     Operator, Generic
+
+
+__all__ = ['VisualStudioStyle']
+
+
+class VisualStudioStyle(Style):
+    name = 'vs'
+    
+    background_color = "#ffffff"
+
+    styles = {
+        Comment:                   "#008000",
+        Comment.Preproc:           "#0000ff",
+        Keyword:                   "#0000ff",
+        Operator.Word:             "#0000ff",
+        Keyword.Type:              "#2b91af",
+        Name.Class:                "#2b91af",
+        String:                    "#a31515",
+
+        Generic.Heading:           "bold",
+        Generic.Subheading:        "bold",
+        Generic.Emph:              "italic",
+        Generic.Strong:            "bold",
+        Generic.EmphStrong:        "bold italic",
+        Generic.Prompt:            "bold",
+
+        Error:                     "border:#FF0000"
+    }