feat(data): add FRED macro indicators as an optional vendor

Surface Federal Reserve Economic Data (rates, inflation, labor, growth) to the
news analyst via a new get_macro_indicators tool and a macro_data vendor
category. Friendly aliases (cpi, unemployment, fed_funds_rate, 10y_treasury,
yield_curve, ...) map to FRED series IDs; raw series IDs are accepted too. The
report gives the latest value, change over the window, and a recent observation
table. Windowing is lookahead-safe (observation_end = curr_date), missing values
are skipped, and a missing FRED_API_KEY surfaces as a clear not-configured
condition through the vendor router rather than a crash.

tradingagents/graph/trading_graph.py

@@ -39,7 +39,8 @@ from tradingagents.agents.utils.agent_utils import (
     get_income_statement,
     get_news,
     get_insider_transactions,
-    get_global_news
+    get_global_news,
+    get_macro_indicators
 )
 
 from .checkpointer import checkpoint_step, clear_checkpoint, get_checkpointer, thread_id
@@ -192,6 +193,7 @@ class TradingAgentsGraph:
                     get_news,
                     get_global_news,
                     get_insider_transactions,
+                    get_macro_indicators,
                 ]
             ),
             "fundamentals": ToolNode(