fix(login): address review feedback on language dropdown PR

- Fix import path: use i18n barrel instead of TranslationContext directly
- Encapsulate localStorage key behind hasStoredLanguage() helper in settingsStore
- Fix pt-BR detection: only map pt-BR to br, pt-PT now returns null correctly
- Add comment linking server SUPPORTED_LANG_CODES to canonical client source
- Extract /api/config inline handler to routes/publicConfig.ts
- Add aria-haspopup, aria-expanded, role=listbox/option, aria-selected to dropdown
- Add 8 tests for detectBrowserLanguage (FE-COMP-I18N-016–023)
- Add 3 tests for setLanguageTransient (FE-STORE-SETTINGS-015–017)

server/src/app.ts

@@ -6,7 +6,7 @@ import path from 'node:path';
 import fs from 'node:fs';
 
 import jwt from 'jsonwebtoken';
-import { JWT_SECRET, DEFAULT_LANGUAGE } from './config';
+import { JWT_SECRET } from './config';
 import { logDebug, logWarn, logError } from './services/auditLog';
 import { enforceGlobalMfaPolicy } from './middleware/mfaPolicy';
 import { authenticate } from './middleware/auth';
@@ -41,6 +41,7 @@ import notificationRoutes from './routes/notifications';
 import shareRoutes from './routes/share';
 import journeyRoutes from './routes/journey';
 import journeyPublicRoutes from './routes/journeyPublic';
+import publicConfigRoutes from './routes/publicConfig';
 import { mcpHandler } from './mcp';
 import { Addon } from './types';
 import { getPhotoProviderConfig } from './services/memories/helpersService';
@@ -194,7 +195,7 @@ export function createApp(): express.Application {
   app.use('/api/trips/:tripId/reservations', reservationsRoutes);
   app.use('/api/trips/:tripId/days/:dayId/notes', dayNotesRoutes);
   app.get('/api/health', (_req: Request, res: Response) => res.json({ status: 'ok' }));
-  app.get('/api/config', (_req: Request, res: Response) => res.json({ defaultLanguage: DEFAULT_LANGUAGE }));
+  app.use('/api/config', publicConfigRoutes);
   app.use('/api', assignmentsRoutes);
   app.use('/api/tags', tagsRoutes);
   app.use('/api/categories', categoriesRoutes);

server/src/config.ts

@@ -102,6 +102,8 @@ export const ENCRYPTION_KEY = _encryptionKey;
 // DEFAULT_LANGUAGE sets the language shown on the login page before the user
 // selects one. Only applies when the user has no saved language preference.
 // Supported values: de, en, es, fr, hu, nl, br, cs, pl, ru, zh, zh-TW, it, ar
+// Must stay in sync with client/src/i18n/supportedLanguages.ts (canonical source).
+// Kept duplicated here because server and client are separate npm packages.
 const SUPPORTED_LANG_CODES = ['de', 'en', 'es', 'fr', 'hu', 'nl', 'br', 'cs', 'pl', 'ru', 'zh', 'zh-TW', 'it', 'ar'];
 const rawDefaultLang = process.env.DEFAULT_LANGUAGE || 'en';
 if (!SUPPORTED_LANG_CODES.includes(rawDefaultLang)) {

server/src/routes/publicConfig.ts

@@ -0,0 +1,10 @@
+import express, { Request, Response } from 'express';
+import { DEFAULT_LANGUAGE } from '../config';
+
+const router = express.Router();
+
+router.get('/', (_req: Request, res: Response) => {
+  res.json({ defaultLanguage: DEFAULT_LANGUAGE });
+});
+
+export default router;