Phase 1: Fix TypeScript compilation — add missing API functions and fix hook signatures

- Add 8 missing API client functions (getBreakPeriods, createBreakPeriod, deleteBreakPeriod, getTips, getParentalLeave, getPlannedDays, createPlannedDay, deletePlannedDay)
- Fix useAnalytics to accept optional childId parameter
- Fix ApiError strict optional properties handling
- Export HeaderProps from Header component
- Update hook tests to use correct data structures and optional parameters

npx tsc --noEmit now passes with zero errors.

Co-Authored-By: Claude Haiku 4.5 <noreply@anthropic.com>

frontend/src/hooks/useAnalytics.test.ts

@@ -18,28 +18,29 @@ describe('useAnalytics', () => {
 
   it('fetches analytics data on mount', async () => {
     const mockData = {
-      workspace_id: 'ws1',
-      total_days: 25,
-      days_used: 10,
-      days_left: 15,
-      projected_left_at_age_4: 50,
+      workspaceId: 'ws1',
+      childId: 'child1',
+      parentProjections: [],
+      combinedDaysUsed: 10,
+      combinedDaysLeft: 15,
+      combinedExpiringAtB4: 50,
     }
 
     vi.mocked(api.getWorkspaceOverview).mockResolvedValue(mockData as any)
 
-    const { result } = renderHook(() => useAnalytics('ws1'))
+    renderHook(() => useAnalytics('ws1', 'child1'))
 
     await act(async () => {
       await new Promise((resolve) => setTimeout(resolve, 0))
     })
 
-    expect(api.getWorkspaceOverview).toHaveBeenCalledWith('ws1')
+    expect(api.getWorkspaceOverview).toHaveBeenCalledWith('ws1', 'child1')
   })
 
   it('handles fetch errors', async () => {
     vi.mocked(api.getWorkspaceOverview).mockRejectedValue(new Error('API error'))
 
-    const { result } = renderHook(() => useAnalytics('ws1'))
+    const { result } = renderHook(() => useAnalytics('ws1', 'child1'))
 
     await act(async () => {
       await new Promise((resolve) => setTimeout(resolve, 0))
@@ -56,10 +57,18 @@ describe('useAnalytics', () => {
     expect(api.getWorkspaceOverview).not.toHaveBeenCalled()
   })
 
+  it('does not fetch when childId is missing', () => {
+    vi.mocked(api.getWorkspaceOverview).mockResolvedValue({} as any)
+
+    renderHook(() => useAnalytics('ws1'))
+
+    expect(api.getWorkspaceOverview).not.toHaveBeenCalled()
+  })
+
   it('provides refresh function', async () => {
     vi.mocked(api.getWorkspaceOverview).mockResolvedValue({} as any)
 
-    const { result } = renderHook(() => useAnalytics('ws1'))
+    const { result } = renderHook(() => useAnalytics('ws1', 'child1'))
 
     await act(async () => {
       await result.current.refresh()