feat: 将额定电压输入改为下拉选择框

将额定电压从数字输入改为预定义选项的下拉选择框，支持常见的电压等级

webui/src/components/ParameterForm.vue

@@ -26,12 +26,11 @@
               <q-card-section>
                 <div class="row q-col-gutter-md">
                   <div class="col-12 col-md-6">
-                    <q-input
+                    <q-select
                       v-model="params.parameter.rated_voltage"
-                      type="number"
+                      :options="voltageOptions"
                       label="额定电压等级 (kV)"
                       hint="输电线路的额定电压"
-                      :rules="[val => val > 0 || '必须大于0']"
                     />
                   </div>
                   <div class="col-12 col-md-6">
@@ -313,7 +312,7 @@ import LogComponent from './Log.vue'
 // 默认参数
 const defaultParams: AllParameters = {
   parameter: {
-    rated_voltage: 750,
+    rated_voltage: '500kV',
     h_c_sag: 14.43,
     h_g_sag: 11.67,
     insulator_c_len: 7.02,
@@ -342,6 +341,11 @@ const result = ref<string | null>(null)
 const error = ref<string | null>(null)
 const logRef = ref<InstanceType<typeof LogComponent> | null>(null)
 
+const voltageOptions = [
+  '110kV', '220kV', '330kV', '500kV', '750kV','1000kV',
+  '±500kV', '±660kV', '±800kV', '±1100kV'
+]
+
 // 数组操作函数
 const addHArm = () => {
   const last = params.parameter.h_arm[params.parameter.h_arm.length - 1] || 100