refactor(frontend): 完成所有组件的内联SVG统一替换为Icon组件

- 扩展 Icon.vue 组件，新增 60+ 图标路径
  - 导航类: arrowRight, arrowLeft, arrowUp, arrowDown, chevronUp, externalLink
  - 状态类: checkCircle, xCircle, exclamationCircle, exclamationTriangle, infoCircle
  - 用户类: user, userCircle, userPlus, users
  - 文档类: document, clipboard, copy, inbox
  - 操作类: download, upload, filter, sort
  - 安全类: key, lock, shield
  - UI类: menu, calendar, home, terminal, gift, creditCard, mail
  - 数据类: chartBar, trendingUp, database, cube
  - 其他: bolt, sparkles, cloud, server, sun, moon, book 等

- 重构 56 个 Vue 组件，用 Icon 组件替换内联 SVG
  - 净减少约 2200 行代码
  - 提升代码可维护性和一致性
  - 统一图标样式和尺寸管理

frontend/src/components/common/LocaleSwitcher.vue

@@ -7,16 +7,12 @@
     >
       <span class="text-base">{{ currentLocale?.flag }}</span>
       <span class="hidden sm:inline">{{ currentLocale?.code.toUpperCase() }}</span>
-      <svg
-        class="h-3.5 w-3.5 text-gray-400 transition-transform duration-200"
+      <Icon
+        name="chevronDown"
+        size="xs"
+        class="text-gray-400 transition-transform duration-200"
         :class="{ 'rotate-180': isOpen }"
-        fill="none"
-        viewBox="0 0 24 24"
-        stroke="currentColor"
-        stroke-width="2"
-      >
-        <path stroke-linecap="round" stroke-linejoin="round" d="M19.5 8.25l-7.5 7.5-7.5-7.5" />
-      </svg>
+      />
     </button>
 
     <transition name="dropdown">
@@ -36,16 +32,7 @@
         >
           <span class="text-base">{{ locale.flag }}</span>
           <span>{{ locale.name }}</span>
-          <svg
-            v-if="locale.code === currentLocaleCode"
-            class="ml-auto h-4 w-4 text-primary-500"
-            fill="none"
-            viewBox="0 0 24 24"
-            stroke="currentColor"
-            stroke-width="2"
-          >
-            <path stroke-linecap="round" stroke-linejoin="round" d="M4.5 12.75l6 6 9-13.5" />
-          </svg>
+          <Icon v-if="locale.code === currentLocaleCode" name="check" size="sm" class="ml-auto text-primary-500" />
         </button>
       </div>
     </transition>
@@ -55,6 +42,7 @@
 <script setup lang="ts">
 import { ref, computed, onMounted, onBeforeUnmount } from 'vue'
 import { useI18n } from 'vue-i18n'
+import Icon from '@/components/icons/Icon.vue'
 import { setLocale, availableLocales } from '@/i18n'
 
 const { locale } = useI18n()