fix: 修复车牌搜索失效，确保所有筛选条件正常

- 后端新增 plate 查询参数支持
- 前端将 filterPlate 传给 API 并加入依赖数组
- 所有筛选条件（部门/项目/主体/车牌/搜索/里程范围）
  均正确传递到后端并触发数据刷新

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

src/server/routes/mileage.ts

@@ -156,6 +156,7 @@ app.get('/monitoring', (c) => {
   const entity = c.req.query('entity') || '';
   const mileageMin = c.req.query('mileageMin') || '';
   const mileageMax = c.req.query('mileageMax') || '';
+  const plate = c.req.query('plate') || '';
 
   let vehicles = monitoringCache.vehicles;
 
@@ -172,6 +173,7 @@ app.get('/monitoring', (c) => {
   if (customer) vehicles = vehicles.filter(v => v.customer === customer);
   if (project) vehicles = vehicles.filter(v => v.project === project);
   if (entity) vehicles = vehicles.filter(v => v.entity === entity);
+  if (plate) vehicles = vehicles.filter(v => v.plate === plate);
   if (mileageMin) vehicles = vehicles.filter(v => v.dailyKm >= Number(mileageMin));
   if (mileageMax) vehicles = vehicles.filter(v => v.dailyKm <= Number(mileageMax));