Fix Issue 3: Add 60s default timeout to OpenAI-compatible backend

patches/llm_backend_timeout.patch

@@ -0,0 +1,13 @@
+--- a/purpose_agent/llm_backend.py
++++ b/purpose_agent/llm_backend.py
+@@ -199,7 +199,7 @@
+     ):
+         from openai import OpenAI
+ 
+         self.model = model
+         self.client = OpenAI(
+             base_url=base_url,
+-            api_key=api_key or os.environ.get("OPENAI_API_KEY"),
++            api_key=api_key or os.environ.get("OPENAI_API_KEY"),
++            timeout=60.0,
+         )