Address findings from the templates code review:
- Fix XSS in admin.html onclick handlers via data attributes
- Fix XSS in 5 edit page signal initializations via JSON serialization
- Fix register.html token exposure by moving to data attribute
- Add entity_icon, quick_notes_toggles, add_form_submit macros
- Replace hardcoded colors with design tokens (warning, error, success)
- Add warning design tokens to CSS theme
- Scope MutationObserver to main element
- Add defer to webauthn.js script tags
- Refactor login/register JS to arrow functions
- Guard lightbox script behind image_url check
- Fix else-if to elif in 5 templates
Add image infrastructure, API, and detail page integration:
- EntityImage domain model with ImageRepository trait
- SQLite storage for images and thumbnails as BLOBs
- Image processing with data URL decoding and thumbnail generation
- REST API: upload, get, delete, thumbnail at /{entity_type}/{id}/image
- resolve_image_url helper for image fallback chains
- image-upload web component for direct upload on detail pages
- Image display with vignette overlay and lightbox viewer
- Template macros: image_thumbnail, readonly_image, lightbox_script
- All 7 detail pages updated with image thumbnails
- Brew images fall back to roast; cup images fall back to cafe then roast
- Delete handler macro extended with optional image cleanup
