fix(mobile-app): align back button to left in import mnemonic page

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Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

frontend/mobile-app/lib/features/auth/presentation/pages/import_mnemonic_page.dart

@@ -275,7 +275,7 @@ class _ImportMnemonicPageState extends ConsumerState<ImportMnemonicPage> {
               child: Container(
                 width: 48,
                 height: 48,
-                alignment: Alignment.center,
+                alignment: Alignment.centerLeft,
                 child: const Icon(
                   Icons.arrow_back_ios,
                   color: Color(0xFF5D4037),