feat(mileage): add daily mileage columns to main export sheet

- '车辆汇总' sheet now includes per-day mileage columns for date ranges
- Daily columns shown as 'MM-DD里程(km)' between base info and summary cols
- Freeze pane fixed at 7 base columns for horizontal scrolling
- '每日明细' sheet retained as detailed backup
- Bump version to 1.1.9

package.json

@@ -1,7 +1,7 @@
 {
   "name": "ln-bi",
   "private": true,
-  "version": "1.1.8",
+  "version": "1.1.9",
   "type": "module",
   "scripts": {
     "dev": "concurrently -n server,client -c blue,green \"npm run dev:server\" \"npm run dev:client\"",