Improve gallery video UX and add upload-to-publish media workflow.

Stage raw files in upload/, publish with make sync-media/publish, and polish the lightbox: autoplay, remembered volume, Escape to close, and image/video icons without poster or caption clutter.

Co-authored-by: Cursor <cursoragent@cursor.com>

app/internal/handlers/handlers.go

@@ -73,8 +73,6 @@ func New(imagesDir, staticDir string, mailCfg *mail.Config) (*Server, error) {
 	} else {
 		log.Print("gallery thumbnails: ready")
 	}
-	// Thumbnail URLs are resolved during gallery.List. Re-list after derivative
-	// generation so newly-created thumbs appear immediately on first load.
 	if refreshed, err := gallery.List(imagesDir); err != nil {
 		log.Printf("gallery refresh after thumbnails: %v", err)
 	} else {