fix: add confirm dialogs for repeater and block deletes

[bobbwal]

Description

Adds confirmation dialogs when deleting repeater items and content blocks in admin content forms to reduce accidental
deletions.

Fixes #626

Changes

• Reuse the shared confirmation dialog component for repeater item deletion.
• Add a separate dialog for block deletion and wire delete handlers to use it.

Testing

• Manual verification in admin content form (repeaters + blocks)
• npm run type-check
• npm run e2e

Unit Tests

• Added/updated unit tests
• All unit tests passing

E2E Tests

• Added/updated E2E tests
• All E2E tests passing

Checklist

• Code follows project conventions
• Tests added/updated and passing
• Type checking passes
• No console errors or warnings
• Documentation updated (if needed)

---

Generated with Claude Code in Conductor