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/pddl.py

@@ -0,0 +1,82 @@
+"""
+    pygments.lexers.pddl
+    ~~~~~~~~~~~~~~~~~~~~
+
+    Lexer for the Planning Domain Definition Language.
+
+    :copyright: Copyright 2006-present by the Pygments team, see AUTHORS.
+    :license: BSD, see LICENSE for details.
+"""
+
+
+from pygments.lexer import RegexLexer, words, include
+from pygments.token import Punctuation, Keyword, Whitespace, Name, Comment, \
+    Operator, Number
+
+
+__all__ = ['PddlLexer']
+
+
+class PddlLexer(RegexLexer):
+    """
+    A PDDL lexer.
+
+    It should support up to PDDL 3.1.
+    """
+
+    name = 'PDDL'
+    aliases = ['pddl']
+    filenames = ['*.pddl']
+    # there doesn't really seem to be a PDDL homepage.
+    url = 'https://en.wikipedia.org/wiki/Planning_Domain_Definition_Language'
+    version_added = '2.19'
+
+    tokens = {
+        'root': [
+            (r'\s+', Whitespace),
+            (r';.*$', Comment.Singleline),
+            include('keywords'),
+            include('builtins'),
+            (r'[()]', Punctuation),
+            (r'[=/*+><-]', Operator),
+            (r'[a-zA-Z][a-zA-Z0-9_-]*', Name),
+            (r'\?[a-zA-Z][a-zA-Z0-9_-]*', Name.Variable),
+            (r'[0-9]+\.[0-9]+', Number.Float),
+            (r'[0-9]+', Number.Integer),
+        ],
+        'keywords': [
+            (words((
+                ':requirements', ':types', ':constants',
+                ':predicates', ':functions', ':action', ':agent',
+                ':parameters', ':precondition', ':effect',
+                ':durative-action', ':duration', ':condition',
+                ':derived', ':domain', ':objects', ':init',
+                ':goal', ':metric', ':length', ':serial', ':parallel',
+                # the following are requirements
+                ':strips', ':typing', ':negative-preconditions',
+                ':disjunctive-preconditions', ':equality',
+                ':existential-preconditions', ':universal-preconditions',
+                ':conditional-effects', ':fluents', ':numeric-fluents',
+                ':object-fluents', ':adl', ':durative-actions',
+                ':continuous-effects', ':derived-predicates',
+                ':time-intial-literals', ':preferences',
+                ':constraints', ':action-costs', ':multi-agent',
+                ':unfactored-privacy', ':factored-privacy',
+                ':non-deterministic'
+                ), suffix=r'\b'), Keyword)
+        ],
+        'builtins': [
+            (words((
+                'define', 'domain', 'object', 'either', 'and',
+                'forall', 'preference', 'imply', 'or', 'exists',
+                'not', 'when', 'assign', 'scale-up', 'scale-down',
+                'increase', 'decrease', 'at', 'over', 'start',
+                'end', 'all', 'problem', 'always', 'sometime',
+                'within', 'at-most-once', 'sometime-after',
+                'sometime-before', 'always-within', 'hold-during',
+                'hold-after', 'minimize', 'maximize',
+                'total-time', 'is-violated'), suffix=r'\b'),
+                Name.Builtin)
+        ]
+    }
+