fix(02): remove custom ViewToolbar; use Schedule-X built-in header

- Remove <ViewToolbar> render and its import from CalendarShell
- Remove createCalendarControlsPlugin import, useState instance, and plugin
  array entry (calendar-controls only served the custom toolbar)
- Delete ViewToolbar.tsx (no longer referenced anywhere)
- Remove calendar-controls mock from CalendarShell.test.tsx
- CSS audit confirmed no rules hide Schedule-X weekday-name row; no CSS changes needed
- All four views (day/week/month-grid/month-agenda) remain; Schedule-X's native
  header exposes them in its own view switcher

apps/pwa/src/components/CalendarShell.test.tsx

@@ -56,41 +56,6 @@ vi.mock('@schedule-x/event-modal', () => ({
   })),
 }))
 
-// Mock @schedule-x/calendar-controls so CalendarShell can create the plugin
-vi.mock('@schedule-x/calendar-controls', () => ({
-  createCalendarControlsPlugin: vi.fn(() => ({
-    name: 'calendarControls',
-    beforeRender: vi.fn(),
-    onRender: vi.fn(),
-    setDate: vi.fn(),
-    setView: vi.fn(),
-    getDate: vi.fn(() => Temporal.Now.plainDateISO()),
-    getView: vi.fn(() => 'month-grid'),
-    setFirstDayOfWeek: vi.fn(),
-    setLocale: vi.fn(),
-    setViews: vi.fn(),
-    setDayBoundaries: vi.fn(),
-    setWeekOptions: vi.fn(),
-    setCalendars: vi.fn(),
-    setMinDate: vi.fn(),
-    setMaxDate: vi.fn(),
-    setMonthGridOptions: vi.fn(),
-    setTimezone: vi.fn(),
-    setResources: vi.fn(),
-    getFirstDayOfWeek: vi.fn(),
-    getLocale: vi.fn(),
-    getViews: vi.fn(() => []),
-    getDayBoundaries: vi.fn(),
-    getWeekOptions: vi.fn(),
-    getCalendars: vi.fn(() => ({})),
-    getMinDate: vi.fn(),
-    getMaxDate: vi.fn(),
-    getMonthGridOptions: vi.fn(),
-    getResources: vi.fn(() => []),
-    getRange: vi.fn(() => null),
-  })),
-}))
-
 // Mock the API client
 vi.mock('../api/client.js', () => ({
   fetchMe: vi.fn(),