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/tlb.py

@@ -0,0 +1,59 @@
+"""
+    pygments.lexers.tlb
+    ~~~~~~~~~~~~~~~~~~~
+
+    Lexers for TL-b.
+
+    :copyright: Copyright 2006-present by the Pygments team, see AUTHORS.
+    :license: BSD, see LICENSE for details.
+"""
+
+from pygments.lexer import RegexLexer, include, words
+from pygments.token import Operator, Name, \
+    Number, Whitespace, Punctuation, Comment
+
+__all__ = ['TlbLexer']
+
+
+class TlbLexer(RegexLexer):
+    """
+    For TL-b source code.
+    """
+
+    name = 'Tl-b'
+    aliases = ['tlb']
+    filenames = ['*.tlb']
+    url = 'https://docs.ton.org/#/overviews/TL-B'
+    version_added = ''
+
+    tokens = {
+        'root': [
+            (r'\s+', Whitespace),
+
+            include('comments'),
+
+            (r'[0-9]+', Number),
+            (words((
+                '+', '-', '*', '=', '?', '~', '.',
+                '^', '==', '<', '>', '<=', '>=', '!='
+            )), Operator),
+            (words(('##', '#<', '#<=')), Name.Tag),
+            (r'#[0-9a-f]*_?', Name.Tag),
+            (r'\$[01]*_?', Name.Tag),
+
+            (r'[a-zA-Z_][0-9a-zA-Z_]*', Name),
+
+            (r'[;():\[\]{}]', Punctuation)
+        ],
+
+        'comments': [
+            (r'//.*', Comment.Singleline),
+            (r'/\*', Comment.Multiline, 'comment'),
+        ],
+        'comment': [
+            (r'[^/*]+', Comment.Multiline),
+            (r'/\*', Comment.Multiline, '#push'),
+            (r'\*/', Comment.Multiline, '#pop'),
+            (r'[*/]', Comment.Multiline),
+        ],
+    }