Make source-use badges read-only display labels

Removing toggle interactivity from use badges — they were confusing
and the wrong place to manage uses. The uses array is now managed
automatically by upload context. Badges are plain spans.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

public/style.css

@@ -1118,13 +1118,6 @@ nav {
 	text-transform: lowercase;
 	font-weight: 600;
 	letter-spacing: 0.02em;
-	cursor: pointer;
-	border: none;
-	transition: opacity 0.1s;
-}
-
-.source-use-badge.source-use-inactive {
-	display: none;
 }
 
 .source-use-grid {