perf(admin): 调小日期滚动条的滚动跨度，避免一次飞太远

- 滚轮/左右箭头: 单次滚动量 200px -> 120px (约2~3个日期卡片)
- 横向条初始长度: 单选 31天(-15~+15)->19天(-8~+10) / 多选 46天(0~45)->29天(0~28)
- 无限扩展步长: 碰到边缘一次+7天 -> +3天(多选额外做了 Math.max(0,start) 防越界)
- 回到今日重置范围 / 快捷选期外扩范围 一并调小

app/components/Admin/AdminMultiDatePicker.vue

@@ -191,7 +191,7 @@ const emit = defineEmits(['update:modelValue', 'change'])
 const dateSelector = ref(null)
 const isFirstDateVisible = ref(false)
 const isLastDateVisible = ref(false)
-const dateRange = ref({ start: 0, end: 45 })
+const dateRange = ref({ start: 0, end: 28 })
 const showCalendar = ref(false)
 const lastClickedDate = ref('')
 
@@ -343,7 +343,7 @@ const applyBatchAction = (action) => {
 const handleWheel = (event) => {
   event.preventDefault()
   if (!dateSelector.value) return
-  const scrollAmount = 200
+  const scrollAmount = 120
   const currentScroll = dateSelector.value.scrollLeft
   dateSelector.value.scrollTo({
     left: event.deltaY > 0 ? currentScroll + scrollAmount : currentScroll - scrollAmount,
@@ -353,7 +353,7 @@ const handleWheel = (event) => {
 
 const scrollDates = (direction) => {
   if (!dateSelector.value) return
-  const scrollAmount = 200
+  const scrollAmount = 120
   const currentScroll = dateSelector.value.scrollLeft
   dateSelector.value.scrollTo({
     left: direction === 'right' ? currentScroll + scrollAmount : currentScroll - scrollAmount,
@@ -364,23 +364,23 @@ const scrollDates = (direction) => {
 const handleScroll = () => {
   if (!dateSelector.value) return
   const { scrollLeft, scrollWidth, clientWidth } = dateSelector.value
-  if (scrollLeft < 50) {
+  if (scrollLeft < 50 && dateRange.value.start > 0) {
     const oldScrollWidth = scrollWidth
-    dateRange.value.start -= 7
+    dateRange.value.start = Math.max(0, dateRange.value.start - 3)
     nextTick(() => {
       const newScrollWidth = dateSelector.value.scrollWidth
       dateSelector.value.scrollLeft += newScrollWidth - oldScrollWidth
     })
   }
   if (scrollWidth - scrollLeft - clientWidth < 50) {
-    dateRange.value.end += 7
+    dateRange.value.end += 3
   }
 }
 
 const scrollToToday = () => {
   if (dateRange.value.start > 0 || dateRange.value.end < 0) {
     dateRange.value.start = 0
-    dateRange.value.end = 30
+    dateRange.value.end = 20
   }
   nextTick(() => {
     if (!dateSelector.value) return