fix(PaginationField): 修复最后一页时上一页按钮显示逻辑

最后一页时根据 submitButton.is_back 控制上一页按钮的显示，保持逻辑一致性

@@ -39,7 +39,15 @@ const props = defineProps({
 
 
 const emit = defineEmits(['prev', 'next', 'submit'])
 const emit = defineEmits(['prev', 'next', 'submit'])
 
 
-const showPrev = computed(() => props.current > 0)
+/**
+ * @description 是否显示上一页按钮（最后一页且 is_back 为 false 时不显示）
+ * @returns {import('vue').ComputedRef<boolean>}
+ */
+const showPrev = computed(() => {
+    // 非最后一页按原逻辑显示；最后一页由 submitButton.is_back 控制显示与否
+    if (!showSubmit.value) return props.current > 0
+    return props.current > 0 && props.submitButton?.is_back !== false
+})
 const showNext = computed(() => props.current < props.total - 1)
 const showNext = computed(() => props.current < props.total - 1)
 const showSubmit = computed(() => props.current === props.total - 1)
 const showSubmit = computed(() => props.current === props.total - 1)