Components: Files and media #13

REQUIREMENTS §22 (Files and media), plus the Lightbox overlay.

• File input
• Instant file upload (custom upload() or built-in XHR with CSRF headers, Laravel 422)
• Additional files upload
• Multiple file input
• Upload progress (+ useUploadQueue)
• Image input
• Avatar upload
• Image cropper (@javaabu/onu/media)
• Drag-and-drop uploader
• Media lister
• Gallery
• Carousel
• Attachment preview
• Document download
• Media player (@javaabu/onu/media)
• Click-to-load video embed
• Lightbox (@javaabu/onu/media)

Merged into claude/amazing-cerf-htnpm8. 213 tests; coverage 99.4% lines / 94.3% branches.

Follow-ups:

• Figma components + Code Connect (Figma kit & token sync #29)
• media-chrome language is page-global (one locale per page)