feat(phishing-detector): Add Kaggle SMS spam dataset loader and evaluation benchmark #11

🎯 Goal

Extend \�eginner/phishing-spam-detector\ by adding an optional --dataset-kaggle\ loader that pulls or ingests the real UCI / Kaggle SMS Spam Collection dataset (5,574 messages) to benchmark against the default synthetic corpus.

📋 Requirements

• Add a helper function in \ rain_and_predict.py\ to load and parse standard \SMSSpamCollection\ tab-separated files.
• Compare Macro-F1 and confusion matrix between synthetic vs Kaggle datasets.
• Update \README.md\ documentation.