fix(frontend): 修复前端审计问题并补充回归测试

frontend/src/router/title.ts

@@ -0,0 +1,12 @@
+/**
+ * 统一生成页面标题，避免多处写入 document.title 产生覆盖冲突。
+ */
+export function resolveDocumentTitle(routeTitle: unknown, siteName?: string): string {
+  const normalizedSiteName = typeof siteName === 'string' && siteName.trim() ? siteName.trim() : 'Sub2API'
+
+  if (typeof routeTitle === 'string' && routeTitle.trim()) {
+    return `${routeTitle.trim()} - ${normalizedSiteName}`
+  }
+
+  return normalizedSiteName
+}