feat: Dynamic Role-Based Dashboard Themes (#3875)

[anshika1179]

Description

This PR addresses issue #3875 by introducing Dynamic Role-Based Dashboard Themes.
It implements a new RoleThemeProvider wrapper (integrated within AllProviders) that hooks into useAuth to determine the user's role and automatically applies a tailored data-role-theme attribute to the root HTML document.

CSS variables in globals.css have been seamlessly updated to respond to this data attribute, ensuring that themes instantly switch:

• Admin: A sleek, professional corporate-blue theme.
• Teacher: A calming professional teal.
• Super-Admin: An elegant gold/dark theme.
• Student: Retains the vibrant, gamified purple Learnova aesthetic.

Fixes #3875

Type of Change

• 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)
• This change requires a 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
• My changes generate no new warnings