Rework workforce sync to per-date storage with rolling window

Replaces the single workforce_rota config snapshot (which was overwritten
on each sync, losing data when switching weeks) with a workforce_daily_shifts
table keyed by date. Sync now covers a rolling today-7 to today+28 window
unconditionally — no date params needed. Each date's record carries a
synced_at timestamp so the UI shows the age of the oldest date in view.
Mid-week viewing works naturally since data is stored per date not per week.
source column reserved for future timesheet replacement of past dates.

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

frontend/src/api.ts

@@ -1,4 +1,4 @@
-import type { BookingsData, StaffMember, GeneralTask, PickupData, TimeReqs, WorkforceRota, Adjustment } from './types'
+import type { BookingsData, StaffMember, GeneralTask, PickupData, TimeReqs, WfDayData, Adjustment } from './types'
 
 const BASE = '/hk-planner/api'
 
@@ -8,7 +8,6 @@ export interface ConfigData {
   pickup_data: PickupData
   general_tasks: GeneralTask[]
   last_reviewed: string
-  workforce_rota: WorkforceRota | null
   workforce_departments: string[]
   adjustments: Adjustment[]
   warn_over_red_hrs: number
@@ -117,8 +116,12 @@ export function putWorkforceDepartments(dept_ids: string[]): Promise<{ ok: boole
   })
 }
 
-export function syncWorkforceRota(start: string, end: string): Promise<WorkforceRota> {
-  return request(`/workforce/sync?start=${start}&end=${end}`, { method: 'POST' })
+export function syncWorkforce(): Promise<{ ok: boolean; from: string; to: string; dates_synced: number }> {
+  return request('/workforce/sync', { method: 'POST' })
+}
+
+export function getWorkforceShifts(start: string, end: string): Promise<Record<string, WfDayData>> {
+  return request(`/workforce/shifts?start=${start}&end=${end}`)
 }
 
 export function getWorkforceStaff(): Promise<{ id: string; name: string }[]> {