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/src/lib/components/git/GitManager.svelte

@@ -27,7 +27,7 @@
     import { onMount } from 'svelte';
     import { t } from '$lib/i18n/index.svelte.js';
     import { Button, HelpTooltip, Icon } from '$lib/ui';
-    import { addToast } from '$lib/toasts.svelte.js';
+    import { notifications } from '$lib/toasts.svelte.js';
     import { resolveDefaultConfig } from '../../../services/git-utils.js';
     import { GitManagerModel } from '$lib/models/GitManagerModel.svelte.ts';
     import { ROUTES } from '$lib/routes';
@@ -255,13 +255,13 @@
                             model.selectVersion(dev.hash, true);
                             const result = await model.getSelectedVersionsDiff();
                             if (result?.diff) {
-                                model.workspaceDiff = result.diff;
+                                model.workspaceDiff = res.diff;
                                 model.activeTab = 'workspace';
-                                addToast($t.git?.viz_diff_ready || 'Dashboard changes loaded for comparison', 'success');
+                                notifications.success($t.git?.viz_diff_ready || 'Dashboard changes loaded for comparison');
                             }
                         }}
                     />
-
+ 
                     {#if model.hasWorkspaceChanges}
                       <section class="flex flex-wrap items-center justify-between gap-3 rounded-lg border border-warning/30 bg-warning-light px-4 py-3" aria-label={$t.git?.workspace_pending_title || 'Несохранённые изменения'}>
                         <div>
@@ -327,7 +327,7 @@
                           if (res?.diff) {
                             model.workspaceDiff = res.diff;
                             model.activeTab = 'workspace';
-                            addToast($t.git?.viz_diff_ready || 'Dashboard changes loaded for comparison', 'success');
+                            notifications.success($t.git?.viz_diff_ready || 'Dashboard changes loaded for comparison');
                           }
                         }}
                         onDeployVersion={(hash) => model.openDeployModal('PREPROD', hash)}