Refactor: Centralize isFileOrUrlEntry Helper Function

Refactor the project to publish a single isFileOrUrlEntry helper from the entry model, replacing duplicated type guards across src/pages/CsvConfigurator.vue, src/pages/GmsConfigurator.vue, src/features/jobs/components/JobEntryList.vue, and src/features/entries/models/Entry.ts. This change promotes shared type safety and cleaner code maintenance.