Replace bare <input type="file"> across all upload locations with a
card-based dropzone component via shared partial. Three visual states:
current server file (thumbnail + Replace/Delete), empty dropzone, and
pending file preview (local FileReader thumbnail + metadata). Delete
actions use data-confirm-message for confirmation dialog.
Centralized as templates/partials/app-file-upload.phtml to prevent
markup drift — documented as deliberate exception to plain-HTML inputs
convention in CLAUDE.md and developer checklist.
Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
