Generate a comprehensive travel itinerary from Nanjing to Changchun, covering flights, accommodation, daily itineraries, attractions, and dining, presented in HTML.
<!DOCTYPE html>
<html>
<head>
<title>旅行行程：南京到长春</title>
<style>
body { font-family: Arial, sans-serif; }
.itinerary { margin: 20px; }
.day { margin-bottom: 20px; }
.header { font-size: 24px; font-weight: bold; }
.sub-header { font-size: 18px; font-weight: bold; }
</style>
</head>
<body>
<div class="itinerary">
<div class="header">旅行行程：南京到长春</div>
<div class="sub-header"...