Redesign notification center to align with AlgoBuddy's learning-focused theme

[sreevyarao]

Is your feature request related to a problem? Please describe.

The current notification button uses a generic notification bell and standard badge design that does not reflect AlgoBuddy's educational and DSA-focused identity.

Describe the solution you'd like

The notification experience should be redesigned to better align with the platform by surfacing learning updates, achievements, streaks, roadmap progress, recommended problems, and newly added resources.

Describe alternatives you've considered

Expected Improvements:

• Theme-consistent notification UI
• Learning-focused notification content
• Better visual alignment with AlgoBuddy branding
• Improved user engagement through educational updates

Additional context

Code of Conduct

• I agree to follow this project's Code of Conduct

[sreevyarao]

@PankajSingh34 Sir, I raised an issue #1350 Redesign notification center to align with AlgoBuddy's learning-focused theme. I would like to work on this issue, please assign this to me.
Thank you!