feat(saas): Phase 2 Admin Web 管理后台 — 完整 CRUD + Dashboard 统计

后端:
- 添加 GET /api/v1/stats/dashboard 聚合统计端点
  (账号数/活跃服务商/今日请求/今日Token用量等7项指标)
- 需要 account:admin 权限

Admin 前端 (Next.js 14 + shadcn/ui + Tailwind + Recharts):
- 设计系统: Dark Mode OLED (#020617 背景, #22C55E CTA)
- 登录页: 双栏布局, 品牌区 + 表单
- Dashboard 布局: Sidebar 导航 + Header + 主内容区
- 仪表盘: 4 统计卡片 + AreaChart 请求趋势 + BarChart Token用量
- 8 个 CRUD 页面:
  - 账号管理 (搜索/角色/状态筛选, 编辑/启用禁用)
  - 服务商 (CRUD + API Key masked)
  - 模型管理 (Provider筛选, CRUD)
  - API 密钥 (创建/撤销, 一次性显示token)
  - 用量统计 (LineChart + BarChart)
  - 中转任务 (状态筛选, 展开详情)
  - 系统配置 (分类Tab, 编辑)
  - 操作日志 (Action筛选, 展开详情)
- 14 个 shadcn 风格 UI 组件 (手写实现)
- 类型化 API 客户端 (SaaSClient, 20+ 方法, 401 自动跳转)
- AuthGuard 路由保护 + useAuth() hook

验证: tsc --noEmit 零 error, pnpm build 13 页面成功, cargo test 21 通过

admin/src/app/(dashboard)/config/page.tsx

@@ -0,0 +1,270 @@
+'use client'
+
+import { useEffect, useState, useCallback } from 'react'
+import {
+  Loader2,
+  Pencil,
+  RotateCcw,
+} from 'lucide-react'
+import { Button } from '@/components/ui/button'
+import { Input } from '@/components/ui/input'
+import { Label } from '@/components/ui/label'
+import { Badge } from '@/components/ui/badge'
+import {
+  Select,
+  SelectContent,
+  SelectItem,
+  SelectTrigger,
+  SelectValue,
+} from '@/components/ui/select'
+import {
+  Table,
+  TableBody,
+  TableCell,
+  TableHead,
+  TableHeader,
+  TableRow,
+} from '@/components/ui/table'
+import {
+  Dialog,
+  DialogContent,
+  DialogHeader,
+  DialogTitle,
+  DialogFooter,
+  DialogDescription,
+} from '@/components/ui/dialog'
+import { Tabs, TabsContent, TabsList, TabsTrigger } from '@/components/ui/tabs'
+import { api } from '@/lib/api-client'
+import { ApiRequestError } from '@/lib/api-client'
+import type { ConfigItem } from '@/lib/types'
+
+const sourceLabels: Record<string, string> = {
+  default: '默认值',
+  env: '环境变量',
+  db: '数据库',
+}
+
+const sourceVariants: Record<string, 'secondary' | 'info' | 'default'> = {
+  default: 'secondary',
+  env: 'info',
+  db: 'default',
+}
+
+export default function ConfigPage() {
+  const [configs, setConfigs] = useState<ConfigItem[]>([])
+  const [loading, setLoading] = useState(true)
+  const [error, setError] = useState('')
+  const [activeTab, setActiveTab] = useState('all')
+
+  // 编辑 Dialog
+  const [editTarget, setEditTarget] = useState<ConfigItem | null>(null)
+  const [editValue, setEditValue] = useState('')
+  const [saving, setSaving] = useState(false)
+
+  const fetchConfigs = useCallback(async (category?: string) => {
+    setLoading(true)
+    setError('')
+    try {
+      const params: Record<string, unknown> = {}
+      if (category && category !== 'all') params.category = category
+      const res = await api.config.list(params)
+      setConfigs(res)
+    } catch (err) {
+      if (err instanceof ApiRequestError) setError(err.body.message)
+      else setError('加载失败')
+    } finally {
+      setLoading(false)
+    }
+  }, [])
+
+  useEffect(() => {
+    fetchConfigs(activeTab)
+  }, [fetchConfigs, activeTab])
+
+  function openEditDialog(config: ConfigItem) {
+    setEditTarget(config)
+    setEditValue(config.current_value !== undefined ? String(config.current_value) : '')
+  }
+
+  async function handleSave() {
+    if (!editTarget) return
+    setSaving(true)
+    try {
+      let parsedValue: string | number | boolean = editValue
+      if (editTarget.value_type === 'number') {
+        parsedValue = parseFloat(editValue) || 0
+      } else if (editTarget.value_type === 'boolean') {
+        parsedValue = editValue === 'true'
+      }
+      await api.config.update(editTarget.id, { value: parsedValue })
+      setEditTarget(null)
+      fetchConfigs(activeTab)
+    } catch (err) {
+      if (err instanceof ApiRequestError) setError(err.body.message)
+    } finally {
+      setSaving(false)
+    }
+  }
+
+  function formatValue(value: unknown): string {
+    if (value === undefined || value === null) return '-'
+    if (typeof value === 'boolean') return value ? 'true' : 'false'
+    return String(value)
+  }
+
+  const categories = ['all', 'auth', 'relay', 'model', 'system']
+
+  return (
+    <div className="space-y-4">
+      {/* 分类 Tabs */}
+      <Tabs value={activeTab} onValueChange={setActiveTab}>
+        <TabsList>
+          {categories.map((cat) => (
+            <TabsTrigger key={cat} value={cat}>
+              {cat === 'all' ? '全部' : cat}
+            </TabsTrigger>
+          ))}
+        </TabsList>
+      </Tabs>
+
+      {error && (
+        <div className="rounded-md bg-destructive/10 border border-destructive/20 px-4 py-3 text-sm text-destructive">
+          {error}
+          <button onClick={() => setError('')} className="ml-2 underline cursor-pointer">关闭</button>
+        </div>
+      )}
+
+      {loading ? (
+        <div className="flex h-64 items-center justify-center">
+          <Loader2 className="h-6 w-6 animate-spin text-muted-foreground" />
+        </div>
+      ) : configs.length === 0 ? (
+        <div className="flex h-64 items-center justify-center text-muted-foreground text-sm">
+          暂无配置项
+        </div>
+      ) : (
+        <Table>
+          <TableHeader>
+            <TableRow>
+              <TableHead>分类</TableHead>
+              <TableHead>Key</TableHead>
+              <TableHead>当前值</TableHead>
+              <TableHead>默认值</TableHead>
+              <TableHead>来源</TableHead>
+              <TableHead>需重启</TableHead>
+              <TableHead>描述</TableHead>
+              <TableHead className="text-right">操作</TableHead>
+            </TableRow>
+          </TableHeader>
+          <TableBody>
+            {configs.map((config) => (
+              <TableRow key={config.id}>
+                <TableCell>
+                  <Badge variant="outline">{config.category}</Badge>
+                </TableCell>
+                <TableCell className="font-mono text-sm">{config.key_path}</TableCell>
+                <TableCell className="font-mono text-sm max-w-[200px] truncate">
+                  {formatValue(config.current_value)}
+                </TableCell>
+                <TableCell className="font-mono text-xs text-muted-foreground max-w-[200px] truncate">
+                  {formatValue(config.default_value)}
+                </TableCell>
+                <TableCell>
+                  <Badge variant={sourceVariants[config.source] || 'secondary'}>
+                    {sourceLabels[config.source] || config.source}
+                  </Badge>
+                </TableCell>
+                <TableCell>
+                  {config.requires_restart ? (
+                    <Badge variant="warning">是</Badge>
+                  ) : (
+                    <span className="text-muted-foreground">否</span>
+                  )}
+                </TableCell>
+                <TableCell className="text-sm text-muted-foreground max-w-[250px] truncate">
+                  {config.description || '-'}
+                </TableCell>
+                <TableCell className="text-right">
+                  <Button variant="ghost" size="icon" onClick={() => openEditDialog(config)} title="编辑">
+                    <Pencil className="h-4 w-4" />
+                  </Button>
+                </TableCell>
+              </TableRow>
+            ))}
+          </TableBody>
+        </Table>
+      )}
+
+      {/* 编辑 Dialog */}
+      <Dialog open={!!editTarget} onOpenChange={() => setEditTarget(null)}>
+        <DialogContent>
+          <DialogHeader>
+            <DialogTitle>编辑配置</DialogTitle>
+            <DialogDescription>
+              修改 {editTarget?.key_path} 的值
+              {editTarget?.requires_restart && (
+                <span className="block mt-1 text-yellow-400 text-xs">
+                  注意: 修改此配置需要重启服务才能生效
+                </span>
+              )}
+            </DialogDescription>
+          </DialogHeader>
+          <div className="space-y-4">
+            <div className="space-y-2">
+              <Label>Key</Label>
+              <Input value={editTarget?.key_path || ''} disabled />
+            </div>
+            <div className="space-y-2">
+              <Label>类型</Label>
+              <Input value={editTarget?.value_type || ''} disabled />
+            </div>
+            <div className="space-y-2">
+              <Label>
+                新值 {editTarget?.default_value !== undefined && (
+                  <span className="text-xs text-muted-foreground ml-2">
+                    (默认: {formatValue(editTarget.default_value)})
+                  </span>
+                )}
+              </Label>
+              {editTarget?.value_type === 'boolean' ? (
+                <Select value={editValue} onValueChange={setEditValue}>
+                  <SelectTrigger>
+                    <SelectValue />
+                  </SelectTrigger>
+                  <SelectContent>
+                    <SelectItem value="true">true</SelectItem>
+                    <SelectItem value="false">false</SelectItem>
+                  </SelectContent>
+                </Select>
+              ) : (
+                <Input
+                  type={editTarget?.value_type === 'number' ? 'number' : 'text'}
+                  value={editValue}
+                  onChange={(e) => setEditValue(e.target.value)}
+                />
+              )}
+            </div>
+          </div>
+          <DialogFooter>
+            <Button
+              variant="outline"
+              onClick={() => {
+                if (editTarget?.default_value !== undefined) {
+                  setEditValue(String(editTarget.default_value))
+                }
+              }}
+            >
+              <RotateCcw className="h-4 w-4 mr-2" />
+              恢复默认
+            </Button>
+            <Button variant="outline" onClick={() => setEditTarget(null)}>取消</Button>
+            <Button onClick={handleSave} disabled={saving}>
+              {saving && <Loader2 className="mr-2 h-4 w-4 animate-spin" />}
+              保存
+            </Button>
+          </DialogFooter>
+        </DialogContent>
+      </Dialog>
+    </div>
+  )
+}