style(footer): 统一多页面底栏按钮样式与排序规则

- 规范 master-order-editor.vue 底栏按钮类型及排序，按钮层级清晰
- 调整 payment-application-form.vue 底栏按钮样式为右对齐并浮动底部
- 统一 invoice-application/receipt-form 页底栏按钮顺序，返回按钮置首
- 所有相关表单页按钮底栏统一采用 sticky 浮动，背景及阴影样式一致
- 修复多个页面按钮缺少 plain 样式导致视觉层级不明
- 按钮间距统一为 12px，底栏内边距调整为 12px 24px
- 调整多个表单页面按钮组从居中对齐改为右对齐，提升操作一致性
- 保留弹窗 footer 按钮布局，不影响各页面独立弹窗交互体验

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

@@ -165,8 +165,8 @@
         /></el-form-item>
       </section-card>
       <div class="receipt-claim-form-page__actions">
-        <el-button type="primary" :loading="submitting" @click="submitClaim">确认</el-button
-        ><el-button :disabled="submitting" @click="goBack">取消</el-button>
+        <el-button :disabled="submitting" @click="goBack">取消</el-button>
+        <el-button type="primary" :loading="submitting" @click="submitClaim">确认</el-button>
       </div>
     </el-form>
 
@@ -471,9 +471,15 @@ export default {
 }
 .receipt-claim-form-page__actions {
   display: flex;
-  justify-content: center;
-  gap: 8px;
-  padding: 16px 0 8px;
+  justify-content: flex-end;
+  gap: 12px;
+  padding: 12px 24px;
+  position: sticky;
+  bottom: 0;
+  z-index: 10;
+  background: #fff;
+  border-top: 1px solid #eff1f7;
+  box-shadow: 0 -2px 8px rgba(0, 0, 0, 0.06);
 }
 .receipt-claim-form-page__dialog-search {
   display: flex;