chore: switch default LLM config to Google Gemini 2.5

Replace placeholder gpt-5-mini model names with gemini-2.5-pro (deep think)
and gemini-2.5-flash (quick think) using the google provider.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

main.py

@@ -8,9 +8,10 @@ load_dotenv()
 
 # Create a custom config
 config = DEFAULT_CONFIG.copy()
-config["deep_think_llm"] = "gpt-5-mini"  # Use a different model
-config["quick_think_llm"] = "gpt-5-mini"  # Use a different model
-config["max_debate_rounds"] = 1  # Increase debate rounds
+config["llm_provider"] = "google"
+config["deep_think_llm"] = "gemini-2.5-pro"
+config["quick_think_llm"] = "gemini-2.5-flash"
+config["max_debate_rounds"] = 1
 
 # Configure data vendors (default uses yfinance, no extra API keys needed)
 config["data_vendors"] = {