feat: 抽测风速改为用户可自定义次数（增删按钮）

- models.rs：新增 spot_check_count 字段（默认 5）
- db.rs：INSERT/SELECT 添加 spotcheckcount 列
- migrations/007：ALTER TABLE weather_data ADD spotcheckcount
- afterbody.js：使用 data.spotCheckCount 动态渲染抽测数据

static/js/afterbody.js

@@ -1,6 +1,5 @@
 const WeatherReport = (function () {
     const BASE_WIND_COUNT = 10;
-    const SPOT_CHECK_COUNT = 5;
 
     const AREA_TYPE_MAP = {
         urban: "城市",
@@ -193,19 +192,20 @@ const WeatherReport = (function () {
             </div>
         </div>`;
 
-        if (data.hasSpotCheckWindSpeed) {
+        const spotCount = data.spotCheckCount || 5;
+        if (data.hasSpotCheckWindSpeed && spotCount > 0) {
             html += `
         <div class="two-column">
             <div class="field full-width">
                 <div class="field-label">抽测风速值：</div>
                 <div class="field-value">
-                    <div class="ten-values">${joinWithComma(data.windSpeed, BASE_WIND_COUNT, BASE_WIND_COUNT + SPOT_CHECK_COUNT)}</div>
+                    <div class="ten-values">${joinWithComma(data.windSpeed, BASE_WIND_COUNT, BASE_WIND_COUNT + spotCount)}</div>
                 </div>
             </div>
             <div class="field full-width">
                 <div class="field-label">抽测风向值：</div>
                 <div class="field-value">
-                    <div class="ten-values">${joinWithComma(data.windDirection, BASE_WIND_COUNT, BASE_WIND_COUNT + SPOT_CHECK_COUNT)}</div>
+                    <div class="ten-values">${joinWithComma(data.windDirection, BASE_WIND_COUNT, BASE_WIND_COUNT + spotCount)}</div>
                 </div>
             </div>
         </div>`;