fix: refactor main.js to remove duplicate code and restore all UI interactions

Author: snehanair-486

web-app/index.html

@@ -432,7 +432,6 @@ <h1 class="hero-title">
 
 <!-- ── Timeline Section ─────────────────────────────────────── -->
 <section class="hero-timeline-section" id="timelineSection">
-  <canvas aria-hidden="true" id="timelineCanvas"></canvas>
   <div class="timeline-background" aria-hidden="true"></div>
   <div aria-hidden="true" class="timeline-orb timeline-orb-one"></div>
   <div aria-hidden="true" class="timeline-orb timeline-orb-two"></div>