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/rrt.py

@@ -0,0 +1,54 @@
+"""
+    pygments.styles.rrt
+    ~~~~~~~~~~~~~~~~~~~
+
+    pygments "rrt" theme, based on Zap and Emacs defaults.
+
+    :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 (
+    Comment,
+    Generic,
+    Keyword,
+    Name,
+    Number,
+    Operator,
+    String,
+    Token,
+)
+
+__all__ = ['RrtStyle']
+
+
+class RrtStyle(Style):
+    """
+    Minimalistic "rrt" theme, based on Zap and Emacs defaults.
+    """
+
+    name = 'rrt'
+
+    background_color = '#000000'
+    highlight_color = '#0000ff'
+
+    styles = {
+        Token:              '#dddddd',
+        Comment:            '#00ff00',
+        Generic.Emph:       '#ffffff',
+        Generic.Heading:    '#ffff00',
+        Generic.Subheading: '#ffff00',
+        Generic.Strong:     '#ffffff',
+        Name.Entity:        '#eedd82',
+        Name.Function:      '#ffff00',
+        Name.Variable:      '#eedd82',
+        Name.Tag:           '#7fffd4',
+        Name.Constant:      '#7fffd4',
+        Keyword:            '#ff0000',
+        Operator.Word:      '#ff0000',
+        Comment.Preproc:    '#e5e5e5',
+        String:             '#87ceeb',
+        Keyword.Type:       '#ee82ee',
+        Number:             '#ff00ff',
+    }