feat(pwa): loading screen in the colours of the last used theme

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

frontend/public/boot-theme.js

@@ -0,0 +1,17 @@
+// Runs before the first paint: the loading screen takes the colours of the theme used last on this
+// device (stored by the app in lib/theme.ts), so a light or orange theme does not start in blue.
+// A file instead of an inline script so the CSP can stay at script-src 'self'.
+(function () {
+  try {
+    var colors = JSON.parse(localStorage.getItem('mindsift_boot_colors') || 'null');
+    if (!colors || typeof colors.bg !== 'string' || typeof colors.accent !== 'string') return;
+    var root = document.documentElement;
+    root.style.setProperty('--boot-bg', colors.bg);
+    root.style.setProperty('--boot-accent', colors.accent);
+    if (typeof colors.onAccent === 'string') root.style.setProperty('--boot-on-accent', colors.onAccent);
+    var meta = document.querySelector('meta[name="theme-color"]');
+    if (meta) meta.setAttribute('content', colors.bg);
+  } catch (e) {
+    // no storage: the loading screen stays blue
+  }
+})();