feat(ui): add navigation header and wire up real page routes

- Add sticky header with book management nav links and logout button
- Replace placeholder page components with real feature imports
- Add login page route to router
- Fix date-time formatting for consistent YYYY-MM-DD HH:mm output

src/features/books/hooks.ts

@@ -0,0 +1,27 @@
+import { useQuery, useMutation, useQueryClient } from "@tanstack/react-query"
+import { getAllBooks } from "@/api/books"
+import { borrowBookForMe } from "@/api/borrows"
+import { toast } from "sonner"
+
+export function useBooks() {
+  return useQuery({
+    queryKey: ["books"],
+    queryFn: getAllBooks,
+    staleTime: 30_000,
+  })
+}
+
+export function useBorrowBook() {
+  const qc = useQueryClient()
+  return useMutation({
+    mutationFn: borrowBookForMe,
+    onSuccess: () => {
+      qc.invalidateQueries({ queryKey: ["books"] })
+      qc.invalidateQueries({ queryKey: ["myBorrows"] })
+      toast.success("借阅成功")
+    },
+    onError: (err) => {
+      toast.error(err instanceof Error ? err.message : "借阅失败")
+    },
+  })
+}