feat: implemented certificate contract

[0xNgoo]

📌 Pull Request Title

Description

Implemented A secure and immutable ink! smart contract for issuing verifiable educational
certificates on Polkadot/Substrate-based blockchains.

Related Issues

Closes #91

Key Functions

Admin Functions

• issue_certificate() - Issue new certificates to students
• add_admin() - Add new administrators (owner only)
• remove_admin() - Remove administrators (owner only)

Public Query Functions

• verify_certificate() - Get certificate details by ID
• has_certificate() - Check if student has certificate for specific course
• get_student_certificates() - Get all certificates for a student
• get_certificate_id() - Get certificate ID for student/course combination
• is_admin() - Check if account is an admin
• get_owner() - Get contract owner address
• get_total_certificates() - Get total number of certificates issued

How to Test

cargo test

Screenshots (if applicable)

Checklist

• My code follows the project's coding style.
• I have tested these changes locally.
• Documentation has been updated where necessary.

[portableDD]

you delete two files, can i know why is the??

to me it look like it only readme you added. you did not do the task assigned to you

[0xNgoo]

They were not needed.

Please, load difference to see code difference or pull code. and review. There were actual changes and i have implemented everything stated in the issue.

You can see the test result also

[0xNgoo]

This.

Please review code properly sir.

[portableDD]

no comment, files changes did not actual show what you did aside from readme.