feat: Add SCSS structure with variables, mixins, and component styles

- Created _variables.scss for color, spacing, typography, and breakpoints.
- Added _mixins.scss for reusable styles including responsive breakpoints, transitions, and box shadows.
- Implemented styles for various components: header, hero, about, contact, education, projects, and skills.
- Established a main.scss file to import component styles and an index.scss for global styles.

package.json

@@ -25,6 +25,7 @@
     "eslint-plugin-react-hooks": "^5.2.0",
     "eslint-plugin-react-refresh": "^0.4.24",
     "globals": "^16.5.0",
+    "sass": "^1.94.0",
     "typescript": "~5.9.3",
     "typescript-eslint": "^8.46.3",
     "vite": "^7.2.2"