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/settlement/components/formal-settlement-editor.vue

@@ -1546,9 +1546,14 @@ export default {
 .formal-editor__page-actions {
   display: flex;
   justify-content: flex-end;
-  padding: 16px 0 4px;
+  padding: 12px 24px;
   border-top: 1px solid #eff1f7;
-  gap: 8px;
+  gap: 12px;
+  position: sticky;
+  bottom: 0;
+  z-index: 10;
+  background: #fff;
+  box-shadow: 0 -2px 8px rgba(0, 0, 0, 0.06);
 }
 .formal-editor__links {
   display: flex;

src/views/settlement/components/pre-settlement-editor.vue

@@ -393,7 +393,7 @@
 
     <template v-if="!pageMode" #footer>
       <el-button @click="visible = false">取消</el-button>
-      <el-button v-if="editable" :loading="saving" @click="saveDraft(false)">保存</el-button>
+      <el-button v-if="editable" type="primary" plain :loading="saving" @click="saveDraft(false)">保存</el-button>
       <el-button
         v-if="editable && hasPermission('pre_settlement_submit')"
         type="primary"
@@ -405,7 +405,7 @@
     </template>
     <div v-if="pageMode" class="pre-settlement-editor__page-actions">
       <el-button @click="visible = false">取消</el-button>
-      <el-button v-if="editable" :loading="saving" @click="saveDraft(false)">保存</el-button>
+      <el-button v-if="editable" type="primary" plain :loading="saving" @click="saveDraft(false)">保存</el-button>
       <el-button
         v-if="editable && hasPermission('pre_settlement_submit')"
         type="primary"
@@ -1529,9 +1529,14 @@ export default {
   &__page-actions {
     display: flex;
     justify-content: flex-end;
-    padding: 16px 0 4px;
+    padding: 12px 24px;
     border-top: 1px solid #eff1f7;
-    gap: 8px;
+    gap: 12px;
+    position: sticky;
+    bottom: 0;
+    z-index: 10;
+    background: #fff;
+    box-shadow: 0 -2px 8px rgba(0, 0, 0, 0.06);
   }
 
   &__form {

src/views/settlement/receivable-payable-detail.vue

@@ -597,7 +597,7 @@
       </div>
       <template #footer>
         <el-button @click="previewDialog.visible = false">取消</el-button>
-        <el-button type="primary" @click="backToGenerateDialog">上一步</el-button>
+        <el-button type="primary" plain @click="backToGenerateDialog">上一步</el-button>
         <el-button type="primary" :loading="previewDialog.submitting" @click="submitGenerateFee">
           提交
         </el-button>