Add fallback for iOS share when copy fails

When clipboard copy fails, shows a text input with the share link
so users can manually select and copy it.

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

index.html

@@ -1220,6 +1220,10 @@
                         <button id="copyLinkBtn" type="button" disabled>Copy link</button>
                         <button id="shareToXBtn" type="button" disabled>Share to X</button>
                     </div>
+                    <div id="shareFallback" style="display: none; margin-top: 12px;">
+                        <p style="font-size: 8px; margin: 0 0 8px 0; color: var(--gb-light);">Sorry, copy doesn't work on your device. Here's the link:</p>
+                        <input id="shareFallbackInput" type="text" readonly style="width: 100%; padding: 8px; font-size: 8px; font-family: 'Press Start 2P', monospace; background: var(--gb-darkest); color: var(--gb-lightest); border: 2px solid var(--gb-light);" />
+                    </div>
                 </div>
 
             </div>