Add real country flags to language selector

- Replace emoji flags with SVG-based country flags
- German flag: Black-Red-Gold (official colors)
- USA flag: Red-White-Blue with stars
- Dynamic flag switching on language change
- Applied to both dashboard and leaderboard
- Database achievements now support English translations
- Extended achievements table with name_en and description_en columns
- Updated API routes to return English translations
- Simplified frontend translation system to use database translations

routes/api.js

@@ -2627,7 +2627,7 @@ router.get('/v1/public/push-status', async (req, res) => {
 router.get('/achievements', async (req, res) => {
     try {
         const result = await pool.query(`
-            SELECT id, name, description, category, icon, points, is_active
+            SELECT id, name, name_en, description, description_en, category, icon, points, is_active
             FROM achievements 
             WHERE is_active = true
             ORDER BY category, points DESC
@@ -2701,7 +2701,9 @@ router.get('/achievements/player/:playerId', async (req, res) => {
             SELECT 
                 a.id,
                 a.name,
+                a.name_en,
                 a.description,
+                a.description_en,
                 a.category,
                 a.icon,
                 a.points,