feat: add Aurora Glass built-in theme

stores/theme-store.ts

@@ -451,11 +451,25 @@ export const useThemeStore = create<ThemeState>()(
       onRehydrateStorage: () => {
         return (state) => {
           if (state) {
-            // Ensure built-in themes are always present after rehydration
+            // Ensure built-in themes are always present after rehydration.
+            // Drop persisted themes that were flagged builtIn but no longer
+            // exist in BUILTIN_THEMES (e.g. a built-in removed from source) so
+            // stale built-ins don't survive as phantom "user" themes.
             const builtInIds = new Set(BUILTIN_THEMES.map(t => t.id));
-            const userThemes = state.installedThemes.filter(t => !builtInIds.has(t.id));
+            const userThemes = state.installedThemes.filter(
+              t => !builtInIds.has(t.id) && !t.builtIn
+            );
             state.installedThemes = [...BUILTIN_THEMES, ...userThemes];
 
+            // If the active theme pointed at a now-removed built-in, fall back
+            // to the default so the UI doesn't reference a missing theme.
+            if (
+              state.activeThemeId &&
+              !state.installedThemes.some(t => t.id === state.activeThemeId)
+            ) {
+              state.activeThemeId = null;
+            }
+
             // Re-apply theme immediately after rehydration
             const resolvedTheme = state.theme === 'system' ? getSystemTheme() : state.theme;
             applyTheme(resolvedTheme);