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/system/user.vue

@@ -221,7 +221,7 @@
               <el-table ref="customerTable" :data="customerList" border @selection-change="handleCustomerSelection"><el-table-column type="selection" width="55" /><el-table-column prop="customerCode" label="客商编码" /><el-table-column prop="fullName" label="客商名称" /></el-table>
             </el-tab-pane>
           </el-tabs>
-          <template #footer><span class="dialog-footer"><el-button type="primary" @click="submitUserForm">保存</el-button><el-button @click="userDialog = false">返回</el-button><el-button v-if="userDialogMode === 'edit'" @click="resetDialogPassword">重置密码</el-button><el-button @click="handleAddRole">添加角色</el-button></span></template>
+          <template #footer><span class="dialog-footer"><el-button type="primary" @click="submitUserForm">保存</el-button><el-button @click="userDialog = false">取消</el-button><el-button v-if="userDialogMode === 'edit'" @click="resetDialogPassword">重置密码</el-button><el-button @click="handleAddRole">添加角色</el-button></span></template>
         </el-dialog>
 
         <!-- 用户角色配置 -->