fix: keep field-count badge hidden until a PDF is uploaded

Compound selector ensures .hidden overrides the badge's display rule,
which previously won on source order and showed an empty pill.

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

Author: vharkins1

frontend/styles.css

@@ -284,6 +284,10 @@ button:hover {
   justify-self: start;
 }
 
+.field-count-badge.hidden {
+  display: none;
+}
+
 .field-count-badge.match {
   background: #e8f3ec;
   border-color: #b9d8c4;