feat(i18n): add language switcher component to navigation

frontend/src/views/ReportView.vue

@@ -21,6 +21,8 @@
       </div>
 
       <div class="header-right">
+        <LanguageSwitcher />
+        <div class="step-divider"></div>
         <div class="workflow-step">
           <span class="step-num">Step 4/5</span>
           <span class="step-name">报告生成</span>
@@ -69,6 +71,7 @@ import Step4Report from '../components/Step4Report.vue'
 import { getProject, getGraphData } from '../api/graph'
 import { getSimulation } from '../api/simulation'
 import { getReport } from '../api/report'
+import LanguageSwitcher from '../components/LanguageSwitcher.vue'
 
 const route = useRoute()
 const router = useRouter()