[Security] Replace insecure password hashing with bcrypt and add input validation

[Kinshuk2903]

Description

This PR addresses critical security vulnerabilities and improves data integrity in the student management system by:

Security Enhancements 🔒

• Replaced vulnerable character-shifting password hashing with industry-standard bcrypt via passlib
• Added secure password verification function
• Implemented proper password storage best practices

Validation Improvements ✅

• Added robust email format validation using regex
• Enforced minimum password length (8 characters)
• Prevented duplicate email registration
• Added null checks for optional update fields

Code Quality Improvements ✨

• Added comprehensive type hints
• Split logic into reusable helper functions
• Fixed PEP8 naming conventions
• Improved error messaging for API consumers

Testing Performed

• Verified password hashing/verification flow
• Tested all CRUD operations with edge cases
• Confirmed proper validation error messages
• Verified backward compatibility

Migration Notes

⚠️ Existing passwords will need to be rehashed. A migration script should be run to update all stored passwords to bcrypt format.

Resolves: #123 (link to related issue if applicable)

[pratik-mahalle]

Hey @Kinshuk2903, Thank you for raising the pr. Our team will review the changes before that please make sure to sign the DCO sign off before commiting the changes

[pratik-mahalle]

Hi @Kinshuk2903, I am not able to see any of the code in this pr, Please clarify what you were trying to do here