style(memory): apply ruff formatting and linting fixes

Auto-fixed linting errors and formatting issues:
- Removed unused imports (F401): pytest, Any, AnalysisType, MemoryType, OutcomeType
- Removed unused variable (F841): hooks variable in test
- Applied consistent formatting across memory service and test files

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

backend/app/services/memory/cache/embedding_cache.py

@@ -405,9 +405,7 @@ class EmbeddingCache:
         count = 0
 
         with self._lock:
-            keys_to_remove = [
-                k for k, v in self._cache.items() if v.model == model
-            ]
+            keys_to_remove = [k for k, v in self._cache.items() if v.model == model]
             for key in keys_to_remove:
                 del self._cache[key]
                 count += 1
@@ -454,9 +452,7 @@ class EmbeddingCache:
             Number of entries removed
         """
         with self._lock:
-            keys_to_remove = [
-                k for k, v in self._cache.items() if v.is_expired()
-            ]
+            keys_to_remove = [k for k, v in self._cache.items() if v.is_expired()]
             for key in keys_to_remove:
                 del self._cache[key]
                 self._stats.expirations += 1