Refactor database connection parameters to use simplified secret keys for improved clarity and maintainability.

Update database configuration to use simplified secret keys for connection parameters.

Update requirements.txt to include mysql-connector-python and python-dotenv for database connectivity and environment variable management.

Refactor data loading to use MySQL database connection; removed CSV decryption function and implemented student grade retrieval from the database.

modified: app.py

modified: app.py

added grade <= 3.0

updated grade

modified: encrypted_grades.csv

modified: encrypted_grades.csv

modified: app.py

Delete fernet_key.txt

Upload requirements.txt

Delete requirements.txt.txt