feat: auto install themes if not present locally with BS Cloud

src/plugins/built-in/themes/index.ts

@@ -10,6 +10,7 @@ const themesPlugin: Plugin = {
 
   run: async (_) => {
     const themeManager = ThemeManager.getInstance();
+    await themeManager.prepareThemeAfterCloudSync();
     await themeManager.initialize();
   },
 };

src/plugins/built-in/themes/theme-manager.ts

@@ -6,6 +6,7 @@ import {
   type LoadedCustomTheme,
   shouldForceThemeAppearance,
 } from "@/types/CustomThemes";
+import { BSPLUS_PENDING_THEME_ENSURE_AFTER_CLOUD_KEY } from "@/seqta/utils/cloudSettingsSync";
 import { settingsState } from "@/seqta/utils/listeners/SettingsState";
 import debounce from "@/seqta/utils/debounce";
 import { themeUpdates } from "@/interface/hooks/ThemeUpdates";
@@ -166,6 +167,31 @@ export class ThemeManager {
     }
   }
 
+  /**
+   * After cloud restore, IndexedDB/theme storage is only reachable from page context (not MV3 SW).
+   * Background sets BSPLUS_PENDING_THEME_ENSURE_AFTER_CLOUD_KEY; we fetch the store JSON here before setTheme().
+   */
+  public async prepareThemeAfterCloudSync(): Promise<void> {
+    try {
+      const snap = await browser.storage.local.get(BSPLUS_PENDING_THEME_ENSURE_AFTER_CLOUD_KEY);
+      const pending = snap[BSPLUS_PENDING_THEME_ENSURE_AFTER_CLOUD_KEY];
+      if (pending === undefined) return;
+
+      await browser.storage.local.remove(BSPLUS_PENDING_THEME_ENSURE_AFTER_CLOUD_KEY);
+
+      if (typeof pending !== "string") return;
+      const id = pending.trim();
+      if (!id) return;
+
+      const existing = (await localforage.getItem(id)) as CustomTheme | null;
+      if (existing) return;
+
+      await this.downloadAndInstallStoreTheme({ id, name: id });
+    } catch (e) {
+      console.warn("[ThemeManager] prepareThemeAfterCloudSync:", e);
+    }
+  }
+
   /**
    * Initialize the theme system and restore previous state
    */