Update README and core files, remove test/debug scripts, improve documentation and robustness

config.py

@@ -3,7 +3,13 @@ from dotenv import load_dotenv
 
 load_dotenv()
 
-GROQ_API_KEY = "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"
+# Get API key from environment variable with fallback
+GROQ_API_KEY = os.getenv("GROQ_API_KEY", "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")
+
+# Validate API key
+if not GROQ_API_KEY or GROQ_API_KEY == "your_api_key_here":
+    raise ValueError("GROQ_API_KEY environment variable is not set or invalid. Please set it in your .env file.")
+
 CONFIDENCE_THRESHOLD = 0.3
 DATE_TOLERANCE_DAYS = 7
 AMOUNT_TOLERANCE_PERCENT = 0.05