Remove unused shareStatus state from Header component

[Copilot]

Addresses feedback that shareStatus state in Header.jsx was defined but never rendered in the UI, unlike the Share component which displays status inline.

Changes

• Removed unused state management: Deleted shareStatus state, shareTimeoutRef ref, and cleanup effect
• Simplified share handler: Share button now only invokes shareHandler with alert callbacks, no state tracking

The Header component intentionally uses alerts for feedback (original UX pattern), while Share.jsx displays status inline. Setting unreferenced state was wasteful.

Before:

const [shareStatus, setShareStatus] = useState({ type: null, message: "" });
// ... 40+ lines of state management that never rendered

After:

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

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