fix: clear entry-form award refs when the callsign is wiped

Live award detection merges pickable refs into award_refs per call, but nothing
dropped them when the call was cleared, so a previous call's ref lingered onto
the next (IT9AOT's ref still showing after typing F4BPO, both listed in the F3
Awards tab). Clear award_refs the moment the callsign field is emptied.

frontend/src/App.tsx

@@ -2672,7 +2672,14 @@ export default function App() {
     // keeps the pre-roll from before this); clearing it discards the take.
     // Recording START happens on blur (leaving the callsign field), NOT here —
     // you may type a call and work it minutes later. Clearing it cancels.
-    if (v.trim() === '') { QSOAudioCancel(); setRecording(false); recordingCallRef.current = ""; }
+    if (v.trim() === '') {
+      QSOAudioCancel(); setRecording(false); recordingCallRef.current = "";
+      // Callsign wiped → drop this contact's award references. They are auto-added
+      // per call (live detection merges pickable refs into award_refs), so without
+      // this they'd carry over to the NEXT call — e.g. IT9AOT's ref lingering when
+      // you then type F4BPO, showing both in the F3 Awards tab.
+      updateDetails({ award_refs: '' });
+    }
     const isEmpty = v.trim() === '';
     if (!isEmpty && !locks.start) {
       // Restart the start time on every callsign change (each keystroke, a