refactor(frontend): remove addToast bridge — migrate all call sites to notifications API

BREAKING: addToast() removed. Use notify() or notifications facade instead.

- Replace addToast(msg, type, duration?) → notify({ message, type, duration? })
- Introduce notifications.success/info/warning/error/show() semantic facade
- Add dismissAllToasts(), timer management (clearTimeout on remove)
- Unify Toast component: single viewport, a11y (role/aria-live by type)
- Migrate 16 models, 2 stores, 38 components, 23 pages (76 files total)
- 147 test files / 3152 tests pass with updated mocks and assertions

frontend/tests/maintenance-form.test.ts

@@ -10,7 +10,7 @@ import { render, screen, fireEvent } from '@testing-library/svelte';
 
 // ── Hoisted mutable state (before vi.mock calls, hoisted to top) ──
 
-const { mockStartMaintenance, mockAddToast, mockEnvStore } = vi.hoisted(() => {
+const { mockStartMaintenance, mockEnvStore } = vi.hoisted(() => {
     // Mutable env store state — tests can change this before render
     let _selectedEnvId = 'env-prod';
 
@@ -23,7 +23,6 @@ const { mockStartMaintenance, mockAddToast, mockEnvStore } = vi.hoisted(() => {
 
     return {
         mockStartMaintenance: vi.fn(),
-        mockAddToast: vi.fn(),
         mockEnvStore: {
             obj: mockEnvStoreObj,
             setSelectedEnvId(id: string) { _selectedEnvId = id; },
@@ -38,7 +37,7 @@ vi.mock('$lib/api/maintenance.js', () => ({
 }));
 
 vi.mock('$lib/toasts.svelte.js', () => ({
-    addToast: mockAddToast,
+    notifications: { success: vi.fn(), error: vi.fn(), info: vi.fn(), warning: vi.fn(), show: vi.fn() },
 }));
 
 vi.mock('$lib/stores/environmentContext.svelte.js', () => ({
@@ -94,6 +93,7 @@ vi.mock('$lib/i18n/index.svelte.js', () => {
 
 // ── Imports (after mocks) ─────────────────────────────────────
 
+import { notifications } from '$lib/toasts.svelte.js';
 import StartMaintenanceForm from '$lib/components/StartMaintenanceForm.svelte';
 
 describe('StartMaintenanceForm', () => {
@@ -153,9 +153,8 @@ describe('StartMaintenanceForm', () => {
         expect(mockStartMaintenance).not.toHaveBeenCalled();
 
         // Error toast should have been shown with the missing environment message
-        expect(mockAddToast).toHaveBeenCalledWith(
+        expect(notifications.error).toHaveBeenCalledWith(
             expect.stringContaining('No environment selected'),
-            'error',
         );
     });
     // #endregion test_validation_fails_without_environment

frontend/tests/maintenance-store.test.ts

@@ -28,8 +28,8 @@ class MockWebSocket {
 vi.stubGlobal('WebSocket', MockWebSocket);
 
 // Mock toasts
-vi.mock('$lib/toasts.svelte.js', () => ({
-    addToast: vi.fn()
+    vi.mock('$lib/toasts.svelte.js', () => ({
+    notifications: { success: vi.fn(), error: vi.fn(), info: vi.fn(), warning: vi.fn(), show: vi.fn() },
 }));
 
 // Mock i18n
@@ -294,21 +294,21 @@ describe('MaintenanceStore', () => {
     });
 
     it('endEvent handles non-Error rejection with fallback message', async () => {
-        const { addToast } = await import('$lib/toasts.svelte.js');
+        const { notifications } = await import('$lib/toasts.svelte.js');
         mockEndMaintenance.mockRejectedValue('string error');
         try {
             await store.endEvent('ev-fail');
         } catch {}
-        expect(addToast).toHaveBeenCalledWith('Failed to end maintenance event', 'error');
+        expect(notifications.error).toHaveBeenCalledWith('Failed to end maintenance event');
     });
 
     it('endAllEvents handles non-Error rejection with fallback message', async () => {
-        const { addToast } = await import('$lib/toasts.svelte.js');
+        const { notifications } = await import('$lib/toasts.svelte.js');
         mockEndAllMaintenance.mockRejectedValue('string error');
         try {
             await store.endAllEvents();
         } catch {}
-        expect(addToast).toHaveBeenCalledWith('Failed to end all events', 'error');
+        expect(notifications.error).toHaveBeenCalledWith('Failed to end all events');
     });
 
     it('WebSocket onerror and onclose callbacks fire', async () => {
@@ -364,24 +364,26 @@ describe('MaintenanceStore', () => {
         expect(mockListDashboardBanners).toHaveBeenCalled();
     });
 
-    it('endEvent without task_id does not call addToast', async () => {
-        const { addToast } = await import('$lib/toasts.svelte.js');
+    it('endEvent without task_id does not show toast', async () => {
+        const { notifications } = await import('$lib/toasts.svelte.js');
         mockEndMaintenance.mockResolvedValue({ status: 'pending' }); // no task_id
         mockListEvents.mockResolvedValue({ active: [], completed: [] });
 
         await store.endEvent('ev-no-task');
 
-        expect(addToast).not.toHaveBeenCalled();
+        expect(notifications.info).not.toHaveBeenCalled();
+        expect(notifications.error).not.toHaveBeenCalled();
     });
 
-    it('endAllEvents without task_id does not call addToast', async () => {
-        const { addToast } = await import('$lib/toasts.svelte.js');
+    it('endAllEvents without task_id does not show toast', async () => {
+        const { notifications } = await import('$lib/toasts.svelte.js');
         mockEndAllMaintenance.mockResolvedValue({ status: 'completed' }); // no task_id
         mockListEvents.mockResolvedValue({ active: [], completed: [] });
 
         await store.endAllEvents();
 
-        expect(addToast).not.toHaveBeenCalled();
+        expect(notifications.info).not.toHaveBeenCalled();
+        expect(notifications.error).not.toHaveBeenCalled();
     });
 });
 // #endregion MaintenanceStoreTests

frontend/tests/maintenance.test.ts

@@ -52,7 +52,7 @@ function resetMockStore() {
 
 // Mock toasts
 vi.mock('$lib/toasts.svelte.js', () => ({
-    addToast: vi.fn()
+    notifications: { success: vi.fn(), error: vi.fn(), info: vi.fn(), warning: vi.fn(), show: vi.fn() },
 }));
 
 // Mock i18n — $t is a derived store, needs subscribe method for Svelte $ prefix