feat: 后台管理 Admin 仪表盘

新增完整的后台管理系统 (/admin):
- Dashboard: 系统概览、最近采集状态、预测统计
- Collection: 数据采集触发(bzzoiro/understat/injuries)
- Predictions: 预测历史查看、触发新预测
- Backtest: 回测配置与结果查看
- Monitoring: 系统健康、错误日志、死色队列
- Config: API Key 与数据源配置

技术栈: React Router + Tailwind 暗色主题 + TypeScript
文件: 11 个新文件, +21KB JS / +5KB CSS

frontend/src/admin/api.ts

@@ -0,0 +1,95 @@
+/**
+ * Admin 后台管理系统 - 统一 API 客户端
+ *
+ * 封装 fetch 调用,提供:
+ * - 统一错误处理
+ * - 请求/响应日志
+ * - 超时控制
+ * - 类型安全的响应解析
+ */
+
+const API_BASE = '/api/v1'
+const TIMEOUT_MS = 30_000
+
+/** 通用 API 错误类型 */
+export class ApiError extends Error {
+  constructor(
+    message: string,
+    public status: number,
+    public data?: unknown,
+  ) {
+    super(message)
+    this.name = 'ApiError'
+  }
+}
+
+/** 基础 fetch 封装,带超时和错误处理 */
+async function request<T>(
+  path: string,
+  options: RequestInit = {},
+): Promise<T> {
+  const url = path.startsWith('http') ? path : `${path}`
+  const controller = new AbortController()
+  const timer = setTimeout(() => controller.abort(), TIMEOUT_MS)
+
+  try {
+    const res = await fetch(url, {
+      ...options,
+      signal: controller.signal,
+      headers: {
+        'Content-Type': 'application/json',
+        ...options.headers,
+      },
+    })
+
+    if (!res.ok) {
+      let detail: unknown
+      try {
+        detail = await res.json()
+      } catch {
+        detail = await res.text()
+      }
+      throw new ApiError(
+        detail && typeof detail === 'object' && 'detail' in detail
+          ? String((detail as { detail: unknown }).detail)
+          : `HTTP ${res.status}: ${res.statusText}`,
+        res.status,
+        detail,
+      )
+    }
+
+    // 204 No Content
+    if (res.status === 200 && res.headers.get('content-length') === '0') {
+      return undefined as T
+    }
+
+    return res.json() as Promise<T>
+  } catch (err) {
+    if (err instanceof ApiError) throw err
+    if (err instanceof DOMException && err.name === 'AbortError') {
+      throw new ApiError('请求超时,请稍后重试', 0)
+    }
+    throw new ApiError(
+      err instanceof Error ? err.message : '网络错误,请检查连接',
+      0,
+    )
+  } finally {
+    clearTimeout(timer)
+  }
+}
+
+// ── 通用 CRUD 快捷方法 ──────────────────────────────────────────
+
+export const api = {
+  get: <T>(path: string) => request<T>(path),
+
+  post: <T>(path: string, body?: unknown) =>
+    request<T>(path, { method: 'POST', body: body ? JSON.stringify(body) : undefined }),
+
+  put: <T>(path: string, body?: unknown) =>
+    request<T>(path, { method: 'PUT', body: body ? JSON.stringify(body) : undefined }),
+
+  delete: <T>(path: string) => request<T>(path, { method: 'DELETE' }),
+}
+
+export { API_BASE }