feat(admin): replace browser confirm() dialogs with native <dialog> modal
- Add styled <dialog id="confirm-dialog"> to base_admin.html — frosted
backdrop, rounded card, Cancel / Confirm buttons
- Add confirmAction(message, form) JS helper — clones OK button to
avoid listener accumulation, calls form.submit() on confirm
- Replace all 5 onclick="return confirm()" across templates with
type="button" + confirmAction(..., this.closest('form'))
· articles.html — Rebuild All
· template_detail.html — Regenerate
· generate_form.html — Generate Articles
· scenario_results.html — Delete scenario
· audience_contacts.html — Remove contact
Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>