[refactor] Improve updates/notifications domain organization (#5590)

* [refactor] Move update-related functionality to platform/updates domain

Reorganizes release management, version compatibility, and notification functionality
following Domain-Driven Design principles, mirroring VSCode's architecture pattern.

- Move releaseService.ts to platform/updates/common/
- Move releaseStore.ts to platform/updates/common/
- Move versionCompatibilityStore.ts to platform/updates/common/
- Move useFrontendVersionMismatchWarning.ts to platform/updates/common/
- Move toastStore.ts to platform/updates/common/
- Move ReleaseNotificationToast.vue to platform/updates/components/
- Move WhatsNewPopup.vue to platform/updates/components/
- Update 25+ import paths across codebase and tests

This creates a cohesive "updates" domain containing all functionality related to
software updates, version checking, release notifications, and user communication
about application state changes.

🤖 Generated with [Claude Code](https://claude.ai/code)

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

* fix imports

---------

Co-authored-by: Claude <noreply@anthropic.com>

src/stores/apiKeyAuthStore.ts

@@ -4,8 +4,8 @@ import { computed, ref, watch } from 'vue'
 
 import { useErrorHandling } from '@/composables/useErrorHandling'
 import { t } from '@/i18n'
+import { useToastStore } from '@/platform/updates/common/toastStore'
 import { useFirebaseAuthStore } from '@/stores/firebaseAuthStore'
-import { useToastStore } from '@/stores/toastStore'
 import { ApiKeyAuthHeader } from '@/types/authTypes'
 import { operations } from '@/types/comfyRegistryTypes'