refactor(dataflows): name the shared modules by what they hold

- interface -> router; symbol_utils -> symbols, which also takes safe_ticker_component
- utils is split: get_current_date to date_window, the HTTP helpers to net
- dataflows imports are absolute; the NoMarketDataError re-export from symbols is gone

tests/test_polymarket.py

@@ -12,7 +12,7 @@ import requests
 
 import tradingagents.dataflows.config as config_module
 import tradingagents.default_config as default_config
-from tradingagents.dataflows import interface, polymarket
+from tradingagents.dataflows import polymarket, router
 from tradingagents.dataflows.config import set_config
 
 
@@ -112,16 +112,16 @@ class PolymarketRoutingTests(unittest.TestCase):
 
     def test_category_routes_to_polymarket(self):
         self.assertEqual(
-            interface.get_category_for_method("get_prediction_markets"),
+            router.get_category_for_method("get_prediction_markets"),
             "prediction_markets",
         )
         set_config({"data_vendors": {"prediction_markets": "polymarket"}})
         with mock.patch.dict(
-            interface.VENDOR_METHODS,
+            router.VENDOR_METHODS,
             {"get_prediction_markets": {"polymarket": lambda *a, **k: "POLY_OK"}},
             clear=False,
         ):
-            out = interface.route_to_vendor("get_prediction_markets", "fed", 5)
+            out = router.route_to_vendor("get_prediction_markets", "fed", 5)
         self.assertEqual(out, "POLY_OK")