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/lexers/iolang.py

@@ -0,0 +1,61 @@
+"""
+    pygments.lexers.iolang
+    ~~~~~~~~~~~~~~~~~~~~~~
+
+    Lexers for the Io language.
+
+    :copyright: Copyright 2006-present by the Pygments team, see AUTHORS.
+    :license: BSD, see LICENSE for details.
+"""
+
+from pygments.lexer import RegexLexer
+from pygments.token import Comment, Operator, Keyword, Name, String, Number, \
+    Whitespace
+
+__all__ = ['IoLexer']
+
+
+class IoLexer(RegexLexer):
+    """
+    For Io (a small, prototype-based programming language) source.
+    """
+    name = 'Io'
+    url = 'http://iolanguage.com/'
+    filenames = ['*.io']
+    aliases = ['io']
+    mimetypes = ['text/x-iosrc']
+    version_added = '0.10'
+    tokens = {
+        'root': [
+            (r'\n', Whitespace),
+            (r'\s+', Whitespace),
+            # Comments
+            (r'//(.*?)$', Comment.Single),
+            (r'#(.*?)$', Comment.Single),
+            (r'/(\\\n)?[*](.|\n)*?[*](\\\n)?/', Comment.Multiline),
+            (r'/\+', Comment.Multiline, 'nestedcomment'),
+            # DoubleQuotedString
+            (r'"(\\\\|\\[^\\]|[^"\\])*"', String),
+            # Operators
+            (r'::=|:=|=|\(|\)|;|,|\*|-|\+|>|<|@|!|/|\||\^|\.|%|&|\[|\]|\{|\}',
+             Operator),
+            # keywords
+            (r'(clone|do|doFile|doString|method|for|if|else|elseif|then)\b',
+             Keyword),
+            # constants
+            (r'(nil|false|true)\b', Name.Constant),
+            # names
+            (r'(Object|list|List|Map|args|Sequence|Coroutine|File)\b',
+             Name.Builtin),
+            (r'[a-zA-Z_]\w*', Name),
+            # numbers
+            (r'(\d+\.?\d*|\d*\.\d+)([eE][+-]?[0-9]+)?', Number.Float),
+            (r'\d+', Number.Integer)
+        ],
+        'nestedcomment': [
+            (r'[^+/]+', Comment.Multiline),
+            (r'/\+', Comment.Multiline, '#push'),
+            (r'\+/', Comment.Multiline, '#pop'),
+            (r'[+/]', Comment.Multiline),
+        ]
+    }