feat: enhance UI styling, add date picker, and clean up inline CSS

app/templates/index.html

@@ -5,7 +5,7 @@ endblock %} {% block content %}
   {% if prev_day %}
   <a href="/day/{{ prev_day }}" class="date-nav-btn">← 前一天</a>
   {% endif %}
-  <h1 class="date-title">{{ current_date }}</h1>
+  <div class="date-title" id="date-picker-trigger">{{ current_date }}</div>
   {% if next_day <= today %}
   <a href="/day/{{ next_day }}" class="date-nav-btn">后一天 →</a>
   {% endif %}
@@ -34,3 +34,24 @@ endblock %} {% block content %}
   {% endfor %}
 </div>
 {% endblock %}
+
+{% block scripts %}
+<script src="/static/js/date-picker.js"></script>
+<script>
+(function() {
+  var trigger = document.getElementById('date-picker-trigger');
+  if (!trigger) return;
+
+  var markedDates = {{ available_dates | tojson }};
+
+  new KamiDatePicker(trigger, {
+    value: {{ current_date | tojson }},
+    maxDate: {{ today | tojson }},
+    markedDates: markedDates,
+    onChange: function(dateStr) {
+      if (dateStr) window.location.href = '/day/' + dateStr;
+    }
+  });
+})();
+</script>
+{% endblock %}