fix(imports): 修复 AI 导入向导多工作表与表头误判

- AI resolve 生成向导时按阶段携带全部 sheetNames，不再只取第一张表
- ImportStageRequest 支持 sheets 数组并兼容旧 sheet；手动重传同步修复
- headerMatches 收窄为单向包含，避免宿舍号被原/新宿舍号反向匹配
- suggestStep 增加入住/换宿显式表头信号，修复入住表误判为换宿
- 预检与预览按工作表逐表解析列映射，兼容异构表头
- 修复预检卡生成向导成功后按钮未复位 loading 的问题
- 补充 mapping/预检/run/ai-chat 多工作表测试

apps/admin/src/components/ImportWizard/ImportWizardModal.tsx

@@ -259,7 +259,7 @@ export const ImportWizardModal: React.FC<ImportWizardModalProps> = ({
     try {
       const detail = await createImportRun(file, {
         source: 'manual',
-        stages: [{ stepKey: activeStepKey, sheet: sheetSelection[activeStepKey]?.[0] }],
+        stages: [{ stepKey: activeStepKey, sheets: sheetSelection[activeStepKey] ?? [] }],
         mapping: { [activeStepKey]: mappingDraft[activeStepKey] ?? {} },
       });
       await loadRun(detail.id);