Refactor: Update index.php and about.php to use unified header template

- index.php: Changed from header01.php to new unified header.php with dark style
- about.php: Changed from header02.php to new unified header.php with light style
- Both pages now use single configurable header template
- Eliminates dependency on separate header files

Test these pages in browser to verify header renders correctly before updating remaining pages

about.php

@@ -1,4 +1,6 @@
-<?php include_once('header02.php');
+<?php
+$headerStyle = 'light';
+include_once('header.php');
 ?>
 
 <style>

index.php

@@ -1,4 +1,6 @@
-<?php include_once('header01.php');
+<?php
+$headerStyle = 'dark';
+include_once('header.php');
 $indemnityPending = false;
 
 if (isset($_SESSION['user_id'])) {