test: dedup sonner mocks and close Toolbar seam-mock gaps

- Replace 10 inline sonner toast mocks with the shared mockSonner() builder.
- Toolbar: add tests for the store-driven undo/redo disabled state and the
  unsaved-changes dot — behaviour the full-store mock previously left
  unasserted.

ha-relevant: yes

frontend/src/components/modals/__tests__/CustomStyleModal.test.tsx

@@ -4,7 +4,7 @@ import { CustomStyleModal } from '../CustomStyleModal'
 import { useThemeStore } from '@/stores/themeStore'
 import { useCanvasStore } from '@/stores/canvasStore'
 
-vi.mock('sonner', () => ({ toast: { success: vi.fn(), error: vi.fn(), info: vi.fn() } }))
+vi.mock('sonner', async () => (await import('@/test/mocks')).mockSonner())
 import { toast } from 'sonner'
 
 describe('CustomStyleModal', () => {

frontend/src/components/modals/__tests__/PendingDevicesModal.test.tsx

@@ -31,7 +31,7 @@ vi.mock('@/api/client', () => ({
   },
 }))
 
-vi.mock('sonner', () => ({ toast: { success: vi.fn(), error: vi.fn(), info: vi.fn() } }))
+vi.mock('sonner', async () => (await import('@/test/mocks')).mockSonner())
 
 vi.mock('@/components/modals/PendingDeviceModal', () => ({
   PendingDeviceModal: ({ device, onApprove }: { device: unknown; onApprove: (d: unknown) => void }) =>

frontend/src/components/modals/__tests__/ScanHistoryModal.test.tsx

@@ -3,7 +3,7 @@ import { render, screen, fireEvent, waitFor } from '@testing-library/react'
 import { ScanHistoryModal } from '../ScanHistoryModal'
 import { TooltipProvider } from '@/components/ui/tooltip'
 
-vi.mock('sonner', () => ({ toast: { success: vi.fn(), error: vi.fn(), warning: vi.fn() } }))
+vi.mock('sonner', async () => (await import('@/test/mocks')).mockSonner())
 vi.mock('@/stores/canvasStore', () => ({
   useCanvasStore: { getState: () => ({ notifyScanDeviceFound: vi.fn() }) },
 }))

frontend/src/components/modals/__tests__/SettingsModal.test.tsx

@@ -2,7 +2,7 @@ import { describe, it, expect, vi, beforeEach } from 'vitest'
 import { render, screen, fireEvent, waitFor } from '@testing-library/react'
 import { SettingsModal } from '../SettingsModal'
 
-vi.mock('sonner', () => ({ toast: { success: vi.fn(), error: vi.fn() } }))
+vi.mock('sonner', async () => (await import('@/test/mocks')).mockSonner())
 vi.mock('@/api/client', () => ({
   settingsApi: {
     get: vi.fn(),

frontend/src/components/modals/__tests__/ThemeModal.test.tsx

@@ -5,7 +5,7 @@ import { useThemeStore } from '@/stores/themeStore'
 import { useCanvasStore } from '@/stores/canvasStore'
 import { THEME_ORDER } from '@/utils/themes'
 
-vi.mock('sonner', () => ({ toast: { success: vi.fn(), error: vi.fn(), info: vi.fn() } }))
+vi.mock('sonner', async () => (await import('@/test/mocks')).mockSonner())
 import { toast } from 'sonner'
 
 describe('ThemeModal', () => {