feat(admin): add book borrowing dialog and root redirect

- Add admin book borrowing dialog with user selection
- Add useAdminBorrowBook mutation with success/error toasts
- Fix sidebar z-index layering on admin layout
- Add RootRedirect component that routes based on admin role

src/api/client.ts

@@ -1,6 +1,7 @@
 import axios, { AxiosError } from "axios"
 import { useAuthStore } from "@/store/authStore"
 import type { ApiResult } from "@/types/api"
+import { extractMessageFromBody } from "@/lib/errors"
 
 function toCamelCase(s: string): string {
   return s.replace(/_([a-z])/g, (_, c) => c.toUpperCase())
@@ -31,15 +32,20 @@ client.interceptors.request.use((config) => {
   return config
 })
 
+function isLoginPage(): boolean {
+  return window.location.pathname === "/login" || window.location.pathname === "/"
+}
+
 client.interceptors.response.use(
   (response) => {
     const body = response.data as ApiResult<unknown>
     if (body.code !== 200) {
       if (body.code === 401) {
         useAuthStore.getState().clearAuth()
-        window.location.href = "/login"
+        if (!isLoginPage()) window.location.href = "/login"
       }
-      throw new Error(body.message || "Request failed")
+      const msg = extractMessageFromBody(body) ?? "请求失败"
+      throw new Error(msg)
     }
     response.data = transformKeys(body) as ApiResult<unknown>
     return response
@@ -52,9 +58,10 @@ client.interceptors.response.use(
     if (data) {
       if (data.code === 401) {
         useAuthStore.getState().clearAuth()
-        window.location.href = "/login"
+        if (!isLoginPage()) window.location.href = "/login"
       }
-      throw new Error(data.message || "Request failed")
+      const msg = extractMessageFromBody(data) ?? "请求失败"
+      throw new Error(msg)
     }
     if (error.code === "ERR_NETWORK" || error.code === "ECONNABORTED") {
       throw new Error("网络连接失败，请检查网络")

src/features/admin/AdminBooksPage.tsx

@@ -21,6 +21,7 @@ import { useAdminBooks, useAddBook, useUpdateBook, useUpdateStock, useDeleteBook
 import { usePlatform } from "@/hooks/usePlatform"
 import { useIsMobile } from "@/hooks/useIsMobile"
 import type { Book } from "@/types/api"
+import { getErrorMessage } from "@/lib/errors"
 
 // ---- Dialog state helpers ----
 interface AddDialog { open: boolean }
@@ -47,7 +48,7 @@ export default function AdminBooksPage() {
   if (error) {
     return (
       <div className="rounded-lg border border-destructive/50 bg-destructive/10 px-4 py-3 text-sm text-destructive">
-        加载失败：{error instanceof Error ? error.message : "未知错误"}
+        加载失败：{getErrorMessage(error)}
       </div>
     )
   }

src/features/admin/AdminBorrowsPage.tsx

@@ -20,6 +20,7 @@ import { useAdminBorrows, useSearchBorrows, useAdminReturnBook } from "./hooks"
 import { usePlatform } from "@/hooks/usePlatform"
 import { useIsMobile } from "@/hooks/useIsMobile"
 import { formatDateTime } from "@/lib/formatters"
+import { getErrorMessage } from "@/lib/errors"
 import type { BorrowInfoVo } from "@/types/api"
 
 export default function AdminBorrowsPage() {
@@ -47,7 +48,7 @@ export default function AdminBorrowsPage() {
   if (error) {
     return (
       <div className="rounded-lg border border-destructive/50 bg-destructive/10 px-4 py-3 text-sm text-destructive">
-        加载失败：{error instanceof Error ? error.message : "未知错误"}
+        加载失败：{getErrorMessage(error)}
       </div>
     )
   }

src/features/admin/hooks.ts

@@ -3,6 +3,7 @@ import { toast } from "sonner"
 import { getAllBooks } from "@/api/books"
 import { addBook, deleteBook, updateBook, updateStock } from "@/api/admin/books"
 import { getAllBorrows, searchBorrows, returnBook, borrowBook as adminBorrowBook } from "@/api/admin/borrows"
+import { getErrorMessage } from "@/lib/errors"
 
 export function useAdminBooks() {
   return useQuery({
@@ -20,7 +21,7 @@ export function useAddBook() {
       toast.success("添加成功")
     },
     onError: (err) => {
-      toast.error(err instanceof Error ? err.message : "添加失败")
+      toast.error(getErrorMessage(err, "添加失败"))
     },
   })
 }
@@ -35,7 +36,7 @@ export function useUpdateBook() {
       toast.success("修改成功")
     },
     onError: (err) => {
-      toast.error(err instanceof Error ? err.message : "修改失败")
+      toast.error(getErrorMessage(err, "修改失败"))
     },
   })
 }
@@ -49,7 +50,7 @@ export function useUpdateStock() {
       toast.success("库存更新成功")
     },
     onError: (err) => {
-      toast.error(err instanceof Error ? err.message : "库存更新失败")
+      toast.error(getErrorMessage(err, "库存更新失败"))
     },
   })
 }
@@ -63,7 +64,7 @@ export function useDeleteBook() {
       toast.success("删除成功")
     },
     onError: (err) => {
-      toast.error(err instanceof Error ? err.message : "删除失败")
+      toast.error(getErrorMessage(err, "删除失败"))
     },
   })
 }
@@ -92,7 +93,7 @@ export function useAdminReturnBook() {
       toast.success("归还成功")
     },
     onError: (err) => {
-      toast.error(err instanceof Error ? err.message : "归还失败")
+      toast.error(getErrorMessage(err, "归还失败"))
     },
   })
 }
@@ -107,7 +108,7 @@ export function useAdminBorrowBook() {
       toast.success("借阅成功")
     },
     onError: (err) => {
-      toast.error(err instanceof Error ? err.message : "借阅失败")
+      toast.error(getErrorMessage(err, "借阅失败"))
     },
   })
 }

src/features/auth/LoginPage.tsx

@@ -9,6 +9,7 @@ import { Button } from "@/components/ui/button"
 import { useAuthStore, isAdminRole } from "@/store/authStore"
 import { login } from "@/api/auth"
 import { setBaseUrl } from "@/api/client"
+import { getErrorMessage } from "@/lib/errors"
 
 export default function LoginPage() {
   const navigate = useNavigate()
@@ -51,7 +52,7 @@ export default function LoginPage() {
       toast.success("登录成功")
       navigate(isAdminRole(result.role) ? "/admin/books" : "/books", { replace: true })
     } catch (err) {
-      toast.error(err instanceof Error ? err.message : "登录失败")
+      toast.error(getErrorMessage(err, "登录失败"))
     } finally {
       setLoading(false)
     }

src/features/books/BooksPage.tsx

@@ -7,6 +7,7 @@ import { useBooks, useBorrowBook } from "./hooks"
 import { useAuthStore } from "@/store/authStore"
 import { usePlatform } from "@/hooks/usePlatform"
 import { useIsMobile } from "@/hooks/useIsMobile"
+import { getErrorMessage } from "@/lib/errors"
 
 export default function BooksPage() {
   const { data: books, isLoading, error } = useBooks()
@@ -22,7 +23,7 @@ export default function BooksPage() {
     return (
       <div className="mx-auto max-w-[1200px] px-4 py-8">
         <div className="rounded-lg border border-destructive/50 bg-destructive/10 px-4 py-3 text-sm text-destructive">
-          加载失败：{error instanceof Error ? error.message : "未知错误"}
+          加载失败：{getErrorMessage(error)}
         </div>
       </div>
     )

src/features/books/hooks.ts

@@ -2,6 +2,7 @@ import { useQuery, useMutation, useQueryClient } from "@tanstack/react-query"
 import { getAllBooks } from "@/api/books"
 import { borrowBookForMe } from "@/api/borrows"
 import { toast } from "sonner"
+import { getErrorMessage } from "@/lib/errors"
 
 export function useBooks() {
   return useQuery({
@@ -21,7 +22,7 @@ export function useBorrowBook() {
       toast.success("借阅成功")
     },
     onError: (err) => {
-      toast.error(err instanceof Error ? err.message : "借阅失败")
+      toast.error(getErrorMessage(err, "借阅失败"))
     },
   })
 }

src/features/borrows/MyBorrowsPage.tsx

@@ -8,6 +8,7 @@ import { useMyBorrows, useReturnBook } from "./hooks"
 import { formatDateTime } from "@/lib/formatters"
 import { usePlatform } from "@/hooks/usePlatform"
 import { useIsMobile } from "@/hooks/useIsMobile"
+import { getErrorMessage } from "@/lib/errors"
 
 export default function MyBorrowsPage() {
   const { data: records, isLoading, error } = useMyBorrows()
@@ -22,7 +23,7 @@ export default function MyBorrowsPage() {
     return (
       <div className="mx-auto max-w-[1200px] px-4 py-8">
         <div className="rounded-lg border border-destructive/50 bg-destructive/10 px-4 py-3 text-sm text-destructive">
-          加载失败：{error instanceof Error ? error.message : "未知错误"}
+          加载失败：{getErrorMessage(error)}
         </div>
       </div>
     )

src/features/borrows/hooks.ts

@@ -1,6 +1,7 @@
 import { useQuery, useMutation, useQueryClient } from "@tanstack/react-query"
 import { getAllMyBorrows, returnBookForMe } from "@/api/borrows"
 import { toast } from "sonner"
+import { getErrorMessage } from "@/lib/errors"
 
 export function useMyBorrows() {
   return useQuery({
@@ -18,7 +19,7 @@ export function useReturnBook() {
       toast.success("归还成功")
     },
     onError: (err) => {
-      toast.error(err instanceof Error ? err.message : "归还失败")
+      toast.error(getErrorMessage(err, "归还失败"))
     },
   })
 }

src/lib/errors.ts

@@ -0,0 +1,33 @@
+/**
+ * Extract a human-readable Chinese error message from anything caught in a try/catch.
+ * Prefers meaningful messages from API responses; falls back to the provided default.
+ */
+export function getErrorMessage(err: unknown, fallback = "操作失败"): string {
+  if (err instanceof Error) return err.message || fallback
+  if (typeof err === "string") return err
+  return fallback
+}
+
+/**
+ * Try to pull an error message from an API response body of unknown shape.
+ * Handles:
+ *   - { code, message }        (ApiResult / custom backend wrapper)
+ *   - { error, message }       (Spring Boot default error attributes)
+ *   - { message }              (plain message)
+ *   - string body
+ */
+export function extractMessageFromBody(body: unknown): string | null {
+  if (!body) return null
+  if (typeof body === "string") return body
+  if (typeof body !== "object") return null
+
+  const d = body as Record<string, unknown>
+
+  // Preferred: message field (ApiResult and Spring Boot both use this)
+  if (typeof d.message === "string" && d.message) return d.message
+
+  // Spring Boot sometimes puts the summary in "error" and detail in "message"
+  if (typeof d.error === "string" && d.error) return d.error
+
+  return null
+}