[refactor] Improve type safety across Vue node widget system

- Create WidgetValue union type for all valid widget values
- Replace 'any' types with proper generic constraints in SimplifiedWidget
- Add runtime validation for widget values in useGraphNodeManager
- Update WidgetSelect to use constrained generics instead of any
- Fix type assertions with proper validation functions
- Ensure SafeWidgetData uses WidgetValue type consistently

This eliminates most 'any' usage while maintaining runtime safety through validation.

src/components/graph/vueWidgets/WidgetSelect.vue

@@ -25,13 +25,13 @@ import {
 } from '@/utils/widgetPropFilter'
 
 const props = defineProps<{
-  widget: SimplifiedWidget<any>
-  modelValue: any
+  widget: SimplifiedWidget<string | number | undefined>
+  modelValue: string | number | undefined
   readonly?: boolean
 }>()
 
 const emit = defineEmits<{
-  'update:modelValue': [value: any]
+  'update:modelValue': [value: string | number | undefined]
 }>()
 
 // Use the composable for consistent widget value handling