fix: 风险规则保存按钮文案改为'保存预览版'

web/src/views/RiskRules.vue

@@ -40,7 +40,7 @@
         <el-tag size="small" type="info">{{ parsed.length }} 条规则</el-tag>
       </div>
       <div style="display:flex;gap:8px">
-        <el-button v-if="snapshotStatus" size="small" type="primary" @click="savePreview" :loading="savingPreview">保存</el-button>
+        <el-button v-if="snapshotStatus" size="small" type="primary" @click="savePreview" :loading="savingPreview">保存预览版</el-button>
         <el-button v-if="hasUnsavedChanges" size="small" @click="resetEditor" type="warning">重置</el-button>
         <el-button v-if="snapshotStatus?.draft.exists" size="small" type="success" @click="publishSnapshot" :loading="publishing">发布正式版</el-button>
         <el-button v-if="snapshotStatus?.draft.exists" size="small" type="danger" @click="discardDraft" :loading="discardingDraft">丢弃预览版</el-button>