Add per-employee dept breakdown via modal popup

Stores per-employee shift costs in wage_actuals_detail (APPROVED shifts
only). Sync fetches employee name map from /api/v2/users alongside dept
names. Clicking any dept row in Weekly or Monthly opens a modal showing
Employee · Shifts · Cost · % of Dept, fetched on demand.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

frontend/src/api.ts

@@ -1,4 +1,4 @@
-import type { DeptActuals, DeptScheduled, NetSalesDay, WageBudget, AppSetting, DeptPct } from './types'
+import type { DeptActuals, DeptScheduled, NetSalesDay, WageBudget, AppSetting, DeptPct, EmployeeDetail } from './types'
 
 const BASE = '/wages/api'
 
@@ -75,6 +75,10 @@ export function saveDeptPcts(pcts: { id: string; pct: number }[]): Promise<{ ok:
   return request('/budgets/dept-pcts', { method: 'PUT', body: JSON.stringify({ pcts }) })
 }
 
+export function getDeptDetail(deptId: string, from: string, to: string): Promise<{ employees: EmployeeDetail[] }> {
+  return request(`/actuals/dept-detail?dept_id=${encodeURIComponent(deptId)}&from=${from}&to=${to}`)
+}
+
 export function downloadExport(view: string, from: string, to: string): void {
   window.open(`${BASE}/export?view=${view}&from=${from}&to=${to}`, '_blank')
 }