feat: add verified course ratings and reviews

[Jidnyasa-P]

Description

Adds a verified course rating and review system for enrolled LearnHub students.

Fixes #18

Type of Change

Please delete options that are not relevant and check the ones that apply:

• 🐛 Bug fix (non-breaking change which fixes an issue)
• ✨ New feature (non-breaking change which adds functionality)
• 💥 Breaking change (fix or feature that would cause existing functionality to not work as expected)
• 📖 Documentation update

Checklist

• My code follows the style guidelines of this project.
• I have performed a self-review of my own code.
• I have commented my code, particularly in hard-to-understand areas.
• I have made corresponding changes to the documentation.
• My changes generate no new warnings or console errors.
• I have tested my changes locally and verified they work as expected.
• Any dependent changes have been merged and published in downstream modules.

Screenshots / Screen Recordings (if applicable)