fix: add missing t() import and fix init order

- app.js: import { t } alongside initI18n, move initI18n() before UI.initTheme()
- sidebar.js: add import { t } from ./i18n.js
- These fix ReferenceError: t is not defined on startup

frontend/js/app.js

@@ -4,7 +4,7 @@
 
 import * as UI from './ui.js';
 import * as Utils from './utils.js';
-import { initI18n } from './i18n.js';
+import { initI18n, t } from './i18n.js';
 
 // Wire up AI toolbar toast (avoids circular import in utils.js)
 window._obsigateShowToast = UI.showToast;
@@ -23,8 +23,8 @@ import { initMermaid, setupFocusMode } from './mermaid-viewer.js';
 // Initialization — mirrors the original app.js init() ordering
 // =========================================================================
 async function init() {
-  UI.initTheme();
   await initI18n();  // Must run before any rendering that uses t()
+  UI.initTheme();
   UI.initHeaderMenu();
   UI.initCustomDropdowns();
 

frontend/js/sidebar.js

@@ -5,6 +5,7 @@ import { populateCustomDropdown, TabManager, closeMobileSidebar, ContextMenuMana
 import { _populateRecentVaultFilter, switchSidebarTab } from './config.js';
 import { el, icon, getVaultIcon, smallBadge, attachTreeItemActionButton, attachTreeItemLongPress, showWelcome, appendHighlightedText } from './viewer.js';
 import { performAdvancedSearch } from './search.js';
+import { t } from './i18n.js';
 
 // ---------------------------------------------------------------------------
 // Vault context switching