Add support for other backends, such as OpenRouter and olama

This aims to offer alternative OpenAI capable api's.
This offers people to experiment with running the application locally

tradingagents/dataflows/interface.py

@@ -703,10 +703,11 @@ def get_YFin_data(
 
 
 def get_stock_news_openai(ticker, curr_date):
-    client = OpenAI()
+    config = get_config()
+    client = OpenAI(base_url=config["openai_backend"])
 
     response = client.responses.create(
-        model="gpt-4.1-mini",
+        model=config["quick_think_llm"],
         input=[
             {
                 "role": "system",
@@ -737,10 +738,11 @@ def get_stock_news_openai(ticker, curr_date):
 
 
 def get_global_news_openai(curr_date):
-    client = OpenAI()
+    config = get_config()
+    client = OpenAI(base_url=config["openai_backend"])
 
     response = client.responses.create(
-        model="gpt-4.1-mini",
+        model=config["quick_think_llm"],
         input=[
             {
                 "role": "system",
@@ -771,10 +773,11 @@ def get_global_news_openai(curr_date):
 
 
 def get_fundamentals_openai(ticker, curr_date):
-    client = OpenAI()
+    config = get_config()
+    client = OpenAI(base_url=config["openai_backend"])
 
     response = client.responses.create(
-        model="gpt-4.1-mini",
+        model=config["quick_think_llm"],
         input=[
             {
                 "role": "system",