fix: 客户饼图省份用车辆表province、区域柱状图用realtime表；加出勤说明

- 后端region-chart新增source参数：vehicle用车辆表，realtime用实时表
- 客户运营地区占比"按省份"改用source=vehicle
- 区域资产分布概览"按省份"继续用source=realtime
- 部门Tab加说明文字：*说明：当天里程>0即为出勤。

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

src/api.ts

@@ -83,8 +83,8 @@ export async function fetchInventoryStats(): Promise<RegionalInventoryStats[]> {
   return fetchJson<RegionalInventoryStats[]>(`${BASE}/inventory-stats`);
 }
 
-export async function fetchRegionChart(groupBy: string, top = 8): Promise<{ name: string; value: number }[]> {
-  return fetchJson<{ name: string; value: number }[]>(`${BASE}/region-chart?groupBy=${groupBy}&top=${top}`);
+export async function fetchRegionChart(groupBy: string, top = 8, source = 'realtime'): Promise<{ name: string; value: number }[]> {
+  return fetchJson<{ name: string; value: number }[]>(`${BASE}/region-chart?groupBy=${groupBy}&top=${top}&source=${source}`);
 }
 
 export async function fetchWeeklyDetail(type: string): Promise<WeeklyDetailItem[]> {