Make PWA install hint dismiss reliable across reloads.

Use delegated clicks, explicit hide state, and init before service worker registration.

Co-authored-by: Cursor <cursoragent@cursor.com>

templates/_pwa_hint.html

@@ -5,6 +5,6 @@
   </div>
   <div class="pwa-hint-actions">
     <button type="button" id="pwa-install-btn" class="viewer-copy-btn" hidden data-i18n="pwa.install">Install</button>
-    <button type="button" id="pwa-hint-dismiss" class="import-report-dismiss" data-i18n-title="actions.dismiss" title="Dismiss">×</button>
+    <button type="button" class="pwa-hint-dismiss" aria-label="Dismiss">×</button>
   </div>
 </div>