fix: 引入 normalizeRateBound 标准化倍率空输入，解决输入清空后过滤失效的问题

frontend/src/views/Websites.vue

@@ -1296,6 +1296,12 @@ const upstreamCounts = computed(() => {
   return counts
 })
 
+function normalizeRateBound(value: unknown): number | null {
+  if (value === null || value === undefined || value === '') return null
+  const parsed = Number(value)
+  return Number.isFinite(parsed) ? parsed : null
+}
+
 const filteredGroupsForModal = computed(() => {
   const query = groupSearchQuery.value.trim().toLowerCase()
   return upstreamGroupOptions.value.filter(item => {
@@ -1314,8 +1320,8 @@ const filteredGroupsForModal = computed(() => {
     }
 
     // 3. 倍率范围过滤
-    const min = groupRateMin.value
-    const max = groupRateMax.value
+    const min = normalizeRateBound(groupRateMin.value)
+    const max = normalizeRateBound(groupRateMax.value)
     if (min !== null || max !== null) {
       const rateVal = parseFloat(String(item.rate))
       if (isNaN(rateVal)) {