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/dataflows/config.py

@@ -1,10 +1,9 @@
 from copy import deepcopy
-from typing import Dict, Optional
 
 import tradingagents.default_config as default_config
 
 # Use default config but allow it to be overridden
-_config: Optional[Dict] = None
+_config: dict | None = None
 
 
 def initialize_config():
@@ -14,7 +13,7 @@ def initialize_config():
         _config = deepcopy(default_config.DEFAULT_CONFIG)
 
 
-def set_config(config: Dict):
+def set_config(config: dict):
     """Update the configuration with custom values.
 
     Dict-valued keys (e.g. ``data_vendors``) are merged one level deep so a
@@ -31,7 +30,7 @@ def set_config(config: Dict):
             _config[key] = value
 
 
-def get_config() -> Dict:
+def get_config() -> dict:
     """Get the current configuration."""
     if _config is None:
         initialize_config()