Phase 2: Tags UI, Custom Fields UI, Notifications Bell

- Tags UI: TagsPage (CRUD, color picker), TagBadge, TagSelector (multi-select, inline creation)
- Custom Fields Backend: model, schema, service, routes, migration 0041
- Custom Fields Frontend: CustomFieldsPage (definitions CRUD), CustomFieldRenderer (dynamic field rendering)
- Custom Fields: _collect_custom_field_definitions() extended to merge DB definitions with plugin definitions
- Notifications Bell: NotificationBell (30s polling, unread badge), NotificationDropdown, NotificationItem
- NotificationBell integrated into TopBar
- Routes: /tags, /settings/custom-fields registered
- Settings nav: Custom Fields entry added
- Menu items: Tags added to automation plugin manifest

app/models/__init__.py

@@ -21,6 +21,7 @@ from app.models.system_settings import SystemSettings
 from app.models.tax import TaxRate
 from app.models.tenant import Tenant
 from app.models.user import User, UserTenant
+from app.models.custom_field_definition import CustomFieldDefinition
 from app.models.workflow import Workflow, WorkflowInstance, WorkflowStepHistory
 
 __all__ = [
@@ -54,6 +55,7 @@ __all__ = [
     "PluginMigration",
     "AIConversation",
     "AIMessage",
+    "CustomFieldDefinition",
     "Workflow",
     "WorkflowInstance",
     "WorkflowStepHistory",