Add LLM long-term memory system

- Implement LLMMemory module with SQLite + FTS5
- Add conversation tracking with context awareness
- Track NPC reputation and interactions
- Integrate memory with LLMBrain for contextual replies
- Add comprehensive test suite (13 tests)
- Update settings with memory_db_path config

src/config/settings.py

@@ -38,6 +38,8 @@ class LLMProviderConfig(BaseModel):
         "You must respond ONLY with the requested format. "
         "Be concise and precise. No explanations unless asked."
     )
+    memory_db_path: str = "data/llm_memory.db"
+    """Path to SQLite database for LLM long-term memory."""
 
 
 class AIConfig(BaseModel):