Fixed issues in MNIST task by Cecilia Wang

[ccc9991113]

1. Model Output Fix: Updated NUM_CLASSES to 10 to correctly predict digits from 0-9.
2. Hyperparameter Adjustments: Increased EPOCHS to 30 for better training and lowered LEARNING_RATE to 0.001 for smoother optimization.
3. Early Stopping: Added early stopping to prevent overfitting and save time.
4. Loss Function: Changed the loss function to sum the batch loss for better control with large batches.
5. Error Metrics: Added F1 Score, Precision, and Recall for more detailed performance evaluation.