fix(web): show dialogs opened from settings on top of the settings page

The settings modal is a full-screen OPAQUE overlay at z-index 500. Dialogs
opened from within it (share, add-account, color picker) share z-index 500 but
sit earlier in the DOM, so they rendered BEHIND the opaque settings page — the
Share button appeared to "do nothing". Drop the settings page to z-index 400 so
real modals stack above it. v79.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

frontend/css/app.css

@@ -1244,6 +1244,10 @@ a { color: var(--primary); text-decoration: none; }
 /* ── Settings Page ──────────────────────────────────────── */
 #modal-settings.modal-overlay {
   align-items: stretch; justify-content: stretch; padding: 0; background: var(--bg-app);
+  /* Full-screen opaque "page". Sit BELOW real modals (z-index 500) so dialogs
+     opened from inside settings — share, add-account, color picker — appear on
+     top instead of behind this page (that's why the Share button "did nothing"). */
+  z-index: 400;
 }
 .settings-page-card {
   width: 100%; height: 100%;

frontend/js/version.js

@@ -1,2 +1,2 @@
 // Increment APP_VERSION with every code change
-export const APP_VERSION = 'v78';
+export const APP_VERSION = 'v79';