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/native.py

@@ -0,0 +1,70 @@
+"""
+    pygments.styles.native
+    ~~~~~~~~~~~~~~~~~~~~~~
+
+    pygments version of my "native" vim theme.
+
+    :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, \
+     Number, Operator, Generic, Token, Whitespace
+
+
+__all__ = ['NativeStyle']
+
+
+class NativeStyle(Style):
+    """
+    Pygments version of the "native" vim theme.
+    """
+    name = 'native'
+    
+    background_color = '#202020'
+    highlight_color = '#404040'
+    line_number_color = '#aaaaaa'
+
+    styles = {
+        Token:              '#d0d0d0',
+        Whitespace:         '#666666',
+
+        Comment:            'italic #ababab',
+        Comment.Preproc:    'noitalic bold #ff3a3a',
+        Comment.Special:    'noitalic bold #e50808 bg:#520000',
+
+        Keyword:            'bold #6ebf26',
+        Keyword.Pseudo:     'nobold',
+        Operator.Word:      'bold #6ebf26',
+
+        String:             '#ed9d13',
+        String.Other:       '#ffa500',
+
+        Number:             '#51b2fd',
+
+        Name.Builtin:       '#2fbccd',
+        Name.Variable:      '#40ffff',
+        Name.Constant:      '#40ffff',
+        Name.Class:         'underline #71adff',
+        Name.Function:      '#71adff',
+        Name.Namespace:     'underline #71adff',
+        Name.Exception:     '#bbbbbb',
+        Name.Tag:           'bold #6ebf26',
+        Name.Attribute:     '#bbbbbb',
+        Name.Decorator:     '#ffa500',
+
+        Generic.Heading:    'bold #ffffff',
+        Generic.Subheading: 'underline #ffffff',
+        Generic.Deleted:    '#ff3a3a',
+        Generic.Inserted:   '#589819',
+        Generic.Error:      '#ff3a3a',
+        Generic.Emph:       'italic',
+        Generic.Strong:     'bold',
+        Generic.EmphStrong: 'bold italic',
+        Generic.Prompt:     '#aaaaaa',
+        Generic.Output:     '#cccccc',
+        Generic.Traceback:  '#ff3a3a',
+
+        Error:              'bg:#e3d2d2 #a61717'
+    }