style(ui): 统一弹窗及独立表单页按钮文案和样式调整

- 将所有弹窗及独立表单页中的“返回”按钮文案统一改为“取消”
- 独立表单页footer的Avue提交与清空按钮去除内置图标，仅保留文字显示
- 更新相关页面和组件按钮文案，包括业务表单、支付表单、客户档案等
- 规范底部操作栏按钮顺序及样式，确保主次操作区分明显
- 修复部分组件页脚按钮文案，保持全站一致性

src/views/payment/invoice-application-form.vue

@@ -417,7 +417,7 @@
       </section-card>
 
       <div class="invoice-form-page__actions">
-        <el-button @click="goBack">返回</el-button>
+        <el-button @click="goBack">取消</el-button>
         <el-button v-if="!readonly" type="primary" plain @click="syncReferenceData">同步</el-button>
         <el-button
           v-if="!readonly && canSave"

src/views/payment/invoice-receipt-form.vue

@@ -240,7 +240,7 @@
       </section-card>
 
       <div class="receipt-form-page__actions">
-        <el-button @click="goBack">返回</el-button>
+        <el-button @click="goBack">取消</el-button>
         <el-button v-if="!readonly" type="primary" plain @click="syncReferenceData">同步</el-button>
         <el-button
           v-if="!readonly && canSave"

src/views/payment/payment-application-form.vue

@@ -328,7 +328,7 @@
         </div>
       </section-card>
       <div class="payment-form-page__actions">
-        <el-button @click="goBack">返回</el-button>
+        <el-button @click="goBack">取消</el-button>
         <el-button v-if="!readonly && canSave" type="primary" plain @click="saveDraft(false)">保存</el-button>
         <el-button
           v-if="!readonly && canSave && hasPermission('payment_application_submit')"