feat: add BDI core agent

Main BDI brain structure implemented. Still some TODOs left, and very
basic implementation (only one belief "user_said(Message)" and every
message is sent straight to a function which is responsible for getting
an LLM response.

ref: N25B-197

pyproject.toml

@@ -14,6 +14,7 @@ dependencies = [
     "pyzmq>=27.1.0",
     "silero-vad>=6.0.0",
     "spade>=4.1.0",
+    "spade-bdi>=0.3.2",
     "torch>=2.8.0",
     "uvicorn>=0.37.0",
 ]