fix(l10n): localize line-bomb row/column chooser labels

The line-bomb axis chooser hardcoded Korean 가로/세로; route them through
new boosterLineRow/boosterLineCol keys (EN: Row/Column).

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

lib/ui/screens/game_screen.dart

@@ -195,11 +195,11 @@ class _GameScreenState extends ConsumerState<GameScreen>
         actions: [
           TextButton(
             onPressed: () => Navigator.of(context).pop(_LineAxis.row),
-            child: const Text('↔ 가로'),
+            child: Text('↔ ${l10n.boosterLineRow}'),
           ),
           TextButton(
             onPressed: () => Navigator.of(context).pop(_LineAxis.col),
-            child: const Text('↕ 세로'),
+            child: Text('↕ ${l10n.boosterLineCol}'),
           ),
         ],
       ),