feat: inline unsubscribe button on email rows

- ✉✕ button appears on rows where the email has a List-Unsubscribe header
- One-click POST / HTTP GET executed automatically; shows ✓ on success
- mailto: targets open the user mail client (we never auto-send email)
- POST /email/{id}/unsubscribe: detects sender, then processes — UserId scoped
- EmailSummaryDto gains IsStarred, HasListUnsubscribe, SupportsOneClick fields
- Both SearchService and CleanupService updated to populate new DTO fields

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

frontend/src/components/EmailRow.jsx

@@ -32,6 +32,22 @@ export default function EmailRow({ email: initial, onRemove }) {
     }
   };
 
+  const handleUnsub = async (e) => {
+    e.stopPropagation();
+    if (acting) return;
+    setActing(true);
+    try {
+      const res = await EmailApi.unsubscribe(email.id);
+      if (res.method === 'mailto') {
+        window.location.href = res.target;
+      } else {
+        setEmail((prev) => ({ ...prev, _unsubDone: true }));
+      }
+    } finally {
+      setActing(false);
+    }
+  };
+
   const handleTrash = async (e) => {
     e.stopPropagation();
     if (acting) return;
@@ -84,6 +100,14 @@ export default function EmailRow({ email: initial, onRemove }) {
             ? act(EmailApi.unstar, { isStarred: false })
             : act(EmailApi.star,   { isStarred: true  })}
         >⭐</button>
+        {email.hasListUnsubscribe && (
+          <button
+            className={`action-btn action-btn--unsub${email._unsubDone ? ' action-btn--done' : ''}`}
+            title={email._unsubDone ? 'Unsubscribed' : 'Unsubscribe'}
+            onClick={handleUnsub}
+            disabled={email._unsubDone}
+          >{email._unsubDone ? '✓' : '✉✕'}</button>
+        )}
         <button
           className="action-btn action-btn--danger"
           title="Move to trash"