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/trac.py

@@ -0,0 +1,66 @@
+"""
+    pygments.styles.trac
+    ~~~~~~~~~~~~~~~~~~~~
+
+    Port of the default trac highlighter design.
+
+    :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, Whitespace
+
+
+__all__ = ['TracStyle']
+
+
+class TracStyle(Style):
+    """
+    Port of the default trac highlighter design.
+    """
+
+    name = 'trac'
+    
+    styles = {
+        Whitespace:             '#bbbbbb',
+        Comment:                'italic #999988',
+        Comment.Preproc:        'bold noitalic #999999',
+        Comment.Special:        'bold #999999',
+
+        Operator:               'bold',
+
+        String:                 '#bb8844',
+        String.Regex:           '#808000',
+
+        Number:                 '#009999',
+
+        Keyword:                'bold',
+        Keyword.Type:           '#445588',
+
+        Name.Builtin:           '#999999',
+        Name.Function:          'bold #990000',
+        Name.Class:             'bold #445588',
+        Name.Exception:         'bold #990000',
+        Name.Namespace:         '#555555',
+        Name.Variable:          '#008080',
+        Name.Constant:          '#008080',
+        Name.Tag:               '#000080',
+        Name.Attribute:         '#008080',
+        Name.Entity:            '#800080',
+
+        Generic.Heading:        '#999999',
+        Generic.Subheading:     '#aaaaaa',
+        Generic.Deleted:        'bg:#ffdddd #000000',
+        Generic.Inserted:       'bg:#ddffdd #000000',
+        Generic.Error:          '#aa0000',
+        Generic.Emph:           'italic',
+        Generic.Strong:         'bold',
+        Generic.EmphStrong:     'bold italic',
+        Generic.Prompt:         '#555555',
+        Generic.Output:         '#888888',
+        Generic.Traceback:      '#aa0000',
+
+        Error:                  'bg:#e3d2d2 #a61717'
+    }