Classification/preprocessing/ishwari-modelspecific

This update includes a renamed branch and model-specific preprocessing for the Census Income dataset, tailored for:

1. Decision Tree

• Label encoding applied to categorical features
• Ordinal encoding for education
• Saved as: census_income_Decision_Tree.csv

2. SVM & MLP

• One-hot encoding for categorical features
• Standardization applied to: age, education, hours-per-week
• Target variable binary encoded (Income)
• Saved as: census_income_SVM_MLP.csv

The notebook preprocessing_ishwari.ipynb has been updated with these changes and has synced updated .gitlab-ci.yml from main.