feat(32-03): create JKResyncButton with colocated loading state

- Extracted resync button from JKSessionScreen
- Local loading state prevents parent re-renders
- memo() wrapper for render optimization
- Preserves original error handling logic

jam-ui/src/components/client/JKResyncButton.js

@@ -0,0 +1,60 @@
+import React, { useState, useCallback, memo } from 'react';
+import { Button, Spinner } from 'reactstrap';
+import { toast } from 'react-toastify';
+import PropTypes from 'prop-types';
+
+/**
+ * Self-contained resync button with colocated loading state.
+ * Loading state changes only re-render this component, not the parent.
+ *
+ * State colocation: https://kentcdodds.com/blog/state-colocation-will-make-your-react-app-faster
+ */
+const JKResyncButton = memo(({ resyncAudio, className }) => {
+  const [loading, setLoading] = useState(false);
+
+  const handleClick = useCallback(async (e) => {
+    e.preventDefault();
+    if (loading) return;
+
+    setLoading(true);
+    try {
+      await resyncAudio();
+      // Silent success (matches legacy behavior)
+    } catch (error) {
+      if (error.message === 'timeout') {
+        toast.error('Audio resync timed out. Please try again.');
+      } else {
+        toast.error('Audio resync failed: ' + (error.message || 'Unknown error'));
+      }
+    } finally {
+      setLoading(false);
+    }
+  }, [resyncAudio, loading]);
+
+  return (
+    <Button
+      className={className || 'btn-custom-outline'}
+      outline
+      size="md"
+      onClick={handleClick}
+      disabled={loading}
+    >
+      {loading ? (
+        <>
+          <Spinner size="sm" /> Resyncing...
+        </>
+      ) : (
+        'Resync'
+      )}
+    </Button>
+  );
+});
+
+JKResyncButton.displayName = 'JKResyncButton';
+
+JKResyncButton.propTypes = {
+  resyncAudio: PropTypes.func.isRequired,
+  className: PropTypes.string
+};
+
+export default JKResyncButton;