Inbox: do not print raw To-addresses in the source chip

When no job board matches, the chip now says Email instead of the
full address; the address stays in the hover title and the opened
message. Board/referral chips are unchanged.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

frontend/src/screens/Inbox.jsx

@@ -225,10 +225,15 @@ async function fetchFormDetail(recordId) {
 function SourceChip({ item }) {
   // The dot carries the partner's brand colour; the label uses theme text —
   // 11px labels in the partner colour failed AA in both themes.
+  // When no board matched, `source` is the raw To-address; keep it out of the
+  // chip — show "Email", and leave the address to the tooltip and the opened
+  // message.
+  const source = String(item.source ?? '')
+  const label = source.includes('@') ? 'Email' : source
   return (
-    <span className="source-chip" style={{ '--chip': item.sourceMeta?.color }} title={item.source}>
+    <span className="source-chip" style={{ '--chip': item.sourceMeta?.color }} title={source}>
       <span className="source-dot" />
-      <span className="source-chip-label">{item.source}</span>
+      <span className="source-chip-label">{label}</span>
     </span>
   )
 }