PWA: install button, one icon badge for Signal, mail and tasks due, share target for files, manifest launch handler

Co-Authored-By: Claude Sonnet 5.5 <noreply@anthropic.com>

public/index.html

@@ -77,6 +77,7 @@
 <script src="/file-actions.js"></script>
 <script src="/signal-view.js"></script>
 <script src="/mail.js"></script>
+<script src="/share.js"></script>
 <script src="/boot.js"></script>
 <script src="/shell.js"></script>
 </body>