Patch 1.5.3, Fixes theme sync issue on first startup

Addresses a bug where the email viewer's dark mode setting was not correctly synchronized with the selected theme on the first application launch.

This ensures a consistent user experience regarding light/dark mode across the application and email viewer.

frontend/src/lib/stores/settings.svelte.ts

@@ -57,6 +57,9 @@ class SettingsStore {
             this.settings.theme = storedTheme;
         }
         
+        // Sync useDarkEmailViewer with theme
+        this.settings.useDarkEmailViewer = this.settings.theme === "dark";
+        
         // Apply the theme
         applyTheme(this.settings.theme);