refactor: migrate Footer component from deprecated makeStyles to MUI v5 styled API

[DevaanshKathuria]

Description

Migrates src/components/Footer/index.jsx from the deprecated @mui/styles makeStyles API to the MUI v5 styled() API as part of the ongoing MUI v4 → v5 migration.

Related Issue

Part of #314 (refactor: Migrate deprecated MUI v4 components to MUI v5)

Motivation and Context

The Footer component was using makeStyles from @mui/styles which is deprecated in MUI v5 and contributes to the peer dependency conflicts seen during npm install. The inline useStyles hook was also instantiated inside the component body which is an anti-pattern. Migrating to styled() removes the deprecated dependency and follows the MUI v5 best practices being adopted across the codebase.

How Has This Been Tested?

• Ran npm run dev successfully after changes
• Footer renders correctly at localhost:5173 with no visual regression
• No new console errors introduced by this change
• Pre-existing warnings are unrelated to this component

Screenshots or GIF (In case of UI changes):

Types of changes

• 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 change)

Checklist:

• My code follows the code style of this project.
• My change requires a change to the documentation.
• I have updated the documentation accordingly.
• I have added tests to cover my changes.
• All new and existing tests passed.