feat(ai): 统一 AI 配置入口到 /admin/ai-settings

## 新增
- 创建 /admin/ai-settings 统一配置页（AiProviderSettingsCard + AiUsageDashboard）
- admin 侧边栏新增"AI 配置"菜单项（权限 AI_CONFIGURE，图标 Sparkles）
- 新增 deleteAiProvider 数据访问层（事务删除 + 自动转移默认）
- 新增 deleteAiProviderAction Server Action（Zod 校验 + 权限校验）
- AiProviderSettingsCard 新增删除按钮（AlertDialog 确认 + destructive 变体）
- 新增 i18n 翻译键（delete/deleteConfirm/deleteSuccess 等，zh-CN + en）

## 移除
- 从 /settings 移除 AI 标签页（原 VALID_TABS 含 "ai"，现仅 4 标签页）
- 从考试页面移除 AI 配置弹窗（Dialog + AiProviderSettingsCard 内嵌）
- 从 ai-provider-selector.tsx 移除配置弹窗（managePanel/manageOpen props）
- 移除 settings-view.tsx 中 canConfigureAi 逻辑和未使用 import

## 变更
- 考试页面"管理"按钮改为 Link 跳转到 /admin/ai-settings
- ai-provider-selector.tsx"管理"按钮改为 Link 跳转到 /admin/ai-settings
- exam-form.tsx 移除 providerDialogOpen/providerDialogKey 状态
- 修正架构文档 004 中 Action 命名（getAiProvidersAction → getAiProviderSummaries 等）

## 架构文档同步
- 004 更新 settings 模块章节（V3 标记/修正 Action 名称/新增 deleteAiProvider）
- 005 新增 deleteAiProviderAction 节点 + /admin/ai-settings 路由

src/modules/settings/components/ai-provider-settings-card.tsx

@@ -6,12 +6,23 @@ import { z } from "zod"
 import { zodResolver } from "@hookform/resolvers/zod"
 import { useForm } from "react-hook-form"
 import { toast } from "sonner"
-import { Loader2, Save, Sparkles } from "lucide-react"
+import { Loader2, Save, Sparkles, Trash2 } from "lucide-react"
 
 import { Card, CardContent, CardDescription, CardFooter, CardHeader, CardTitle } from "@/shared/components/ui/card"
 import { Button } from "@/shared/components/ui/button"
 import { Checkbox } from "@/shared/components/ui/checkbox"
 import { Label } from "@/shared/components/ui/label"
+import {
+  AlertDialog,
+  AlertDialogAction,
+  AlertDialogCancel,
+  AlertDialogContent,
+  AlertDialogDescription,
+  AlertDialogFooter,
+  AlertDialogHeader,
+  AlertDialogTitle,
+  AlertDialogTrigger,
+} from "@/shared/components/ui/alert-dialog"
 import {
   Form,
   FormControl,
@@ -28,7 +39,7 @@ import {
   SelectTrigger,
   SelectValue,
 } from "@/shared/components/ui/select"
-import { getAiProviderSummaries, testAiProviderAction, upsertAiProviderAction, type AiProviderSummary } from "@/modules/settings/actions"
+import { deleteAiProviderAction, getAiProviderSummaries, testAiProviderAction, upsertAiProviderAction, type AiProviderSummary } from "@/modules/settings/actions"
 
 const ProviderSchema = z.enum(["zhipu", "openai", "gemini", "custom"])
 
@@ -242,6 +253,44 @@ export function AiProviderSettingsCard({
     })
   }
 
+  const handleDelete = () => {
+    const id = form.getValues("id")
+    if (!id?.trim()) {
+      toast.error(t("deleteNeedSelect"))
+      return
+    }
+    startTransition(async () => {
+      const result = await deleteAiProviderAction({ id: id.trim() })
+      if (result.success) {
+        toast.success(result.message ?? t("deleteSuccess"))
+        const summariesResult = await getAiProviderSummaries()
+        if (summariesResult.success && summariesResult.data) {
+          const rows = summariesResult.data
+          setProviders(rows)
+          onProvidersChanged?.(rows)
+          if (rows.length > 0) {
+            const next = rows[0]
+            setSelectedId(next.id)
+            form.reset({
+              id: next.id,
+              provider: next.provider,
+              baseUrl: next.baseUrl ?? "",
+              model: next.model,
+              apiKey: "",
+              isDefault: next.isDefault,
+            })
+          } else {
+            resetToNew()
+          }
+        } else {
+          resetToNew()
+        }
+      } else {
+        toast.error(result.message ?? t("deleteFailure"))
+      }
+    })
+  }
+
   return (
     <Card>
       <CardHeader>
@@ -339,32 +388,56 @@ export function AiProviderSettingsCard({
             />
 
             <CardFooter className="flex justify-between border-t px-0 pt-4">
-              <Button type="button" variant="outline" onClick={handleTest} disabled={isPending || testStatus === "testing"}>
-                {testStatus === "testing" ? (
-                  <>
-                    <Loader2 className="mr-2 h-4 w-4 animate-spin" />
-                    {t("testing")}
-                  </>
-                ) : (
-                  <>
-                    <Sparkles className="mr-2 h-4 w-4" />
-                    {t("test")}
-                  </>
-                )}
-              </Button>
-              <Button type="button" onClick={form.handleSubmit(onSubmit)} disabled={isPending}>
-                {isPending ? (
-                  <>
-                    <Loader2 className="mr-2 h-4 w-4 animate-spin" />
-                    {t("saving")}
-                  </>
-                ) : (
-                  <>
-                    <Save className="mr-2 h-4 w-4" />
-                    {t("save")}
-                  </>
-                )}
-              </Button>
+              <AlertDialog>
+                <AlertDialogTrigger asChild>
+                  <Button
+                    type="button"
+                    variant="destructive"
+                    disabled={isPending || !form.getValues("id")?.trim()}
+                  >
+                    <Trash2 className="mr-2 h-4 w-4" />
+                    {t("delete")}
+                  </Button>
+                </AlertDialogTrigger>
+                <AlertDialogContent>
+                  <AlertDialogHeader>
+                    <AlertDialogTitle>{t("deleteConfirmTitle")}</AlertDialogTitle>
+                    <AlertDialogDescription>{t("deleteConfirmDescription")}</AlertDialogDescription>
+                  </AlertDialogHeader>
+                  <AlertDialogFooter>
+                    <AlertDialogCancel>{t("deleteCancel")}</AlertDialogCancel>
+                    <AlertDialogAction onClick={handleDelete}>{t("deleteConfirm")}</AlertDialogAction>
+                  </AlertDialogFooter>
+                </AlertDialogContent>
+              </AlertDialog>
+              <div className="flex gap-2">
+                <Button type="button" variant="outline" onClick={handleTest} disabled={isPending || testStatus === "testing"}>
+                  {testStatus === "testing" ? (
+                    <>
+                      <Loader2 className="mr-2 h-4 w-4 animate-spin" />
+                      {t("testing")}
+                    </>
+                  ) : (
+                    <>
+                      <Sparkles className="mr-2 h-4 w-4" />
+                      {t("test")}
+                    </>
+                  )}
+                </Button>
+                <Button type="button" onClick={form.handleSubmit(onSubmit)} disabled={isPending}>
+                  {isPending ? (
+                    <>
+                      <Loader2 className="mr-2 h-4 w-4 animate-spin" />
+                      {t("saving")}
+                    </>
+                  ) : (
+                    <>
+                      <Save className="mr-2 h-4 w-4" />
+                      {t("save")}
+                    </>
+                  )}
+                </Button>
+              </div>
             </CardFooter>
           </div>
         </Form>