fix: 修复侧边栏拖拽区域的国际化文案和鼠标样式

- 添加 toggleSidebar 的中英文翻译
- 移除无效的拖拽鼠标样式，改为 pointer
- 使用 i18n 替换硬编码的英文文本

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

frontend/src/components/ui/sidebar/SidebarRail.vue

@@ -2,11 +2,13 @@
 import type { HTMLAttributes } from "vue"
 import { cn } from "@/lib/utils"
 import { useSidebar } from "./utils"
+import { useI18n } from "vue-i18n"
 
 const props = defineProps<{
   class?: HTMLAttributes["class"]
 }>()
 
+const { t } = useI18n()
 const { toggleSidebar } = useSidebar()
 </script>
 
@@ -14,16 +16,15 @@ const { toggleSidebar } = useSidebar()
   <button
     data-sidebar="rail"
     data-slot="sidebar-rail"
-    aria-label="Toggle Sidebar"
+    :aria-label="t('common.toggleSidebar')"
     :tabindex="-1"
-    title="Toggle Sidebar"
+    :title="t('common.toggleSidebar')"
     :class="cn(
       'hover:after:bg-sidebar-border absolute inset-y-0 z-20 hidden w-4 -translate-x-1/2 transition-all ease-linear group-data-[side=left]:-right-4 group-data-[side=right]:left-0 after:absolute after:inset-y-0 after:left-1/2 after:w-[2px] sm:flex',
-      'in-data-[side=left]:cursor-w-resize in-data-[side=right]:cursor-e-resize',
-      '[[data-side=left][data-state=collapsed]_&]:cursor-e-resize [[data-side=right][data-state=collapsed]_&]:cursor-w-resize',
       'hover:group-data-[collapsible=offcanvas]:bg-sidebar group-data-[collapsible=offcanvas]:translate-x-0 group-data-[collapsible=offcanvas]:after:left-full',
       '[[data-side=left][data-collapsible=offcanvas]_&]:-right-2',
       '[[data-side=right][data-collapsible=offcanvas]_&]:-left-2',
+      'cursor-pointer',
       props.class,
     )"
     @click="toggleSidebar"

frontend/src/plugins/i18n/en.json

@@ -77,7 +77,8 @@
     "admin": "Admin",
     "agent": "Agent",
     "basicPlan": "Basic Plan",
-    "normal": "Normal"
+    "normal": "Normal",
+    "toggleSidebar": "Toggle Sidebar"
   },
   "premium": {
     "premium": "premium",

frontend/src/plugins/i18n/zh.json

@@ -77,7 +77,8 @@
     "admin": "管理员",
     "agent": "代理商",
     "basicPlan": "基础版",
-    "normal": "正常"
+    "normal": "正常",
+    "toggleSidebar": "切换侧边栏"
   },
   "premium": {
     "premium": "会员计划",