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/borrows/hooks.ts

@@ -0,0 +1,24 @@
+import { useQuery, useMutation, useQueryClient } from "@tanstack/react-query"
+import { getAllMyBorrows, returnBookForMe } from "@/api/borrows"
+import { toast } from "sonner"
+
+export function useMyBorrows() {
+  return useQuery({
+    queryKey: ["myBorrows"],
+    queryFn: getAllMyBorrows,
+  })
+}
+
+export function useReturnBook() {
+  const qc = useQueryClient()
+  return useMutation({
+    mutationFn: returnBookForMe,
+    onSuccess: () => {
+      qc.invalidateQueries({ queryKey: ["myBorrows"] })
+      toast.success("归还成功")
+    },
+    onError: (err) => {
+      toast.error(err instanceof Error ? err.message : "归还失败")
+    },
+  })
+}