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/abap.py

@@ -0,0 +1,32 @@
+"""
+    pygments.styles.abap
+    ~~~~~~~~~~~~~~~~~~~~
+
+    ABAP workbench like style.
+
+    :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
+
+
+__all__ = ['AbapStyle']
+
+
+class AbapStyle(Style):
+    name = 'abap'
+
+    styles = {
+        Comment:                'italic #888',
+        Comment.Special:        '#888',
+        Keyword:                '#00f',
+        Operator.Word:          '#00f',
+        Name:                   '#000',
+        Number:                 '#3af',
+        String:                 '#5a2',
+
+        Error:                  '#F00',
+    }