chore(lint): make the repository ruff-clean under the strict select

Clear the deferred full-repo lint backlog so the whole tree passes the strict
ruff select (E,W,F,I,B,UP,C4,SIM). Mechanical fixes dominate: import sorting,
pep585/604 annotations, dropped dead imports, and whitespace. The few semantic
changes are behavior-preserving: declare __all__ on the agent_utils and
alpha_vantage re-export hubs; expand 'from x import *' to explicit names; use
immutable tuple defaults instead of mutable list defaults; contextlib.suppress
for try/except/pass; and narrow an over-broad assertRaises.

tradingagents/llm_clients/factory.py

@@ -1,11 +1,11 @@
-from typing import Optional
 
 from .base_client import BaseLLMClient
 
+
 def create_llm_client(
     provider: str,
     model: str,
-    base_url: Optional[str] = None,
+    base_url: str | None = None,
     **kwargs,
 ) -> BaseLLMClient:
     """Create an LLM client for the specified provider.