fix: bug at relative navbar links (freeCodeCamp-2025-Summer-Hackathon#96)

Author: Vallayah

frontend/src/components/Header.jsx

@@ -23,13 +23,13 @@ const Header = () => {
               <a href='/' className='nav-link'>
                 Home
               </a>
-              <a href='#' className='nav-link'>
+              <a href='/ideas/add/' className='nav-link'>
                 Post Idea
               </a>
-              <a href='#about-project-section' className='nav-link'>
+              <a href='/#about-project-section' className='nav-link'>
                 Project
               </a>
-              <a href='#about-team-section' className='nav-link'>
+              <a href='/#about-team-section' className='nav-link'>
                 Team
               </a>
             </div>