Refactor Header component to use shareHandler utility

[Copilot]

The Header component duplicated error handling logic that already exists in the shareHandler utility function, creating maintenance burden and violating DRY principles.

Changes

• Replaced inline error handling (feature detection, try-catch, error categorization) with shareHandler call using callbacks
• Preserved alert-based user feedback for clipboard copy and error cases (Header lacks visual status display unlike Share component)
• Reduced Share button handler from 45 lines to 17 lines

Before

onClick={async () => {
  try {
    if (!navigator.share && (!navigator.clipboard || !navigator.clipboard.writeText)) {
      throw new Error("Share and Clipboard APIs are not supported");
    }
    if (navigator.share) {
      await navigator.share({ title, url });
      // ...
    } else {
      await navigator.clipboard.writeText(url);
      // ...
    }
  } catch (error) {
    if (error.name === "AbortError") { /* ... */ }
    if (error.name === "NotAllowedError") { /* ... */ }
    // ...
  }
}}

After

onClick={async () => {
  await shareHandler({
    shareUrl: window.location.href,
    shareTitle: document.title,
    onSuccess: (message) => {
      setShareStatus({ type: "success", message });
      if (message.includes("clipboard")) alert(message);
      setTimeout(() => setShareStatus({ type: null, message: "" }), 3000);
    },
    onError: (message) => {
      setShareStatus({ type: "error", message });
      alert(message.includes("Permission denied") ? message : `Share failed: ${message}`);
      setTimeout(() => setShareStatus({ type: null, message: "" }), 5000);
    },
  });
}}

This follows the same pattern as Share.jsx (lines 12-36) and centralizes error handling in the utility function.

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