feat: 侧边栏分组图标与导航样式优化

- 分组支持 icon 字段，可按名称自动匹配或手动选择
- 左侧导航与总览卡片显示彩色 SVG 图标
- 优化侧栏链接圆角与选中态样式

Co-authored-by: Cursor <cursoragent@cursor.com>

templates/index.html

@@ -1,4 +1,5 @@
 {% extends "base.html" %}
+{% from "macros/group_icon.html" import render as group_icon %}
 {% block title %}导航 · 本地导航{% endblock %}
 {% block body %}
 <div class="app-shell">
@@ -35,7 +36,11 @@
     </div>
     {% for group, services in grouped %}
     <div class="sidebar-section">
-      <h2>{{ group.name }}</h2>
+      <h2 class="sidebar-group-title">
+        {{ group_icon(group.resolve_icon_key()) }}
+        <span class="sidebar-group-name">{{ group.name }}</span>
+      </h2>
+      <div class="sidebar-links">
       {% for svc in services %}
       <a
         href="#"
@@ -48,11 +53,12 @@
         data-embed-kind="{{ (svc.embed_kind or '')|e }}"
         data-service-id="{{ svc.id }}"
         data-name="{{ svc.name | e }}"
-        >{{ svc.name }}</a
+        ><span class="nav-link-text">{{ svc.name }}</span></a
       >
       {% else %}
-      <div class="hint" style="padding: 0 1rem">该分组下暂无服务</div>
+      <div class="hint sidebar-empty">该分组下暂无服务</div>
       {% endfor %}
+      </div>
     </div>
     {% else %}
     <div class="hint" style="padding: 1rem">
@@ -74,7 +80,10 @@
     <div class="service-dashboard" id="service-dashboard">
       {% for group, services in grouped %}
       <section class="dash-section">
-        <h3 class="dash-section-title">{{ group.name }}</h3>
+        <h3 class="dash-section-title">
+          {{ group_icon(group.resolve_icon_key()) }}
+          <span>{{ group.name }}</span>
+        </h3>
         <div class="service-card-grid">
           {% for svc in services %}
           <button