feat(admin): 仪表盘次级概览卡接真数据(A5) — 8卡聚合,存储卡诚实占位

- Dashboard.tsx 去掉占位块 → OverviewSection; 新增 admin/modules/dashboard/(MiniMetric/useDashboardExtras/overviewMetrics/OverviewSection)
- 8卡用现有 lib/api 导出: LLM组/RAG文档/自动化/已装插件(含toolCount)/用户/网关请求/LLM调用+子代理/存储(缺只读端点→诚实占位)
- 端点报错→值'—'+徽标'端点报错'+hint后端原文(不崩不伪造)
- 仅碰 Dashboard.tsx+dashboard/*, 未动 api.ts/types.ts(避免并发冲突)
- 前端 npm run build 绿(156 modules)

frontend/web/src/admin/modules/dashboard/MiniMetric.tsx

@@ -0,0 +1,54 @@
+import type { ReactNode } from "react";
+import { Icon, type IconName } from "../../../components/Icon";
+import { Tag, type TagTone } from "../../../components/primitives";
+import { navigateAdmin, type AdminSectionId } from "../../router";
+
+/** Honest per-card state: real data landed / still loading / endpoint failed /
+ *  no endpoint exists in lib/api.ts (a placeholder, never a fabricated value). */
+export type MetricState = "ok" | "loading" | "error" | "placeholder";
+
+/** One derived overview card (design/10 §4: 卡片多而全, 详情在各独立页面). */
+export interface MiniMetricSpec {
+  icon: IconName;
+  label: string;
+  value: string;
+  hint: string;
+  state: MetricState;
+  /** Admin module this card drills down to; absent = not a link. */
+  section?: AdminSectionId;
+}
+
+const STATE_BADGE: Record<MetricState, { label: string; tone: TagTone }> = {
+  ok: { label: "已接入", tone: "ok" },
+  loading: { label: "加载中", tone: "neutral" },
+  error: { label: "端点报错", tone: "err" },
+  placeholder: { label: "占位", tone: "warn" },
+};
+
+export function MiniMetric({ icon, label, value, hint, state, section }: MiniMetricSpec): ReactNode {
+  const badge = STATE_BADGE[state];
+  const body = (
+    <>
+      <div className="flex items-center gap-1.5 text-xs text-[var(--mu-text-lo)]">
+        <Icon name={icon} size={14} />
+        <span className="truncate">{label}</span>
+        <Tag tone={badge.tone} className="ml-auto shrink-0">{badge.label}</Tag>
+      </div>
+      <div className="mt-1.5 text-lg font-semibold leading-tight">{value}</div>
+      <div className="mt-0.5 break-words text-xs text-[var(--mu-text-lo)]">{hint}</div>
+    </>
+  );
+  const base =
+    "rounded-[var(--mu-radius)] border border-[var(--mu-glass-border)] bg-[var(--mu-surface-3)]/60 p-3";
+  if (!section) return <div className={base}>{body}</div>;
+  return (
+    <button
+      type="button"
+      title="点击下钻"
+      onClick={() => navigateAdmin(section)}
+      className={`${base} text-left transition-all duration-200 ease-[var(--mu-spring)] hover:border-[var(--mu-accent)]/50`}
+    >
+      {body}
+    </button>
+  );
+}