feat: implement subscription import/export with CSV and JSON support

src/navigation/AppNavigator.tsx

@@ -21,6 +21,8 @@ import SettingsScreen from '../screens/SettingsScreen';
 import AccountingExportScreen from '../screens/AccountingExportScreen';
 import WebhookSettingsScreen from '../screens/WebhookSettingsScreen';
 import ErrorDashboardScreen from '../screens/ErrorDashboardScreen';
+import ImportScreen from '../screens/ImportScreen';
+import ExportScreen from '../screens/ExportScreen';
 import AdminDashboardScreen from '../screens/AdminDashboardScreen';
 import InvoiceListScreen from '../screens/InvoiceListScreen';
 import InvoiceDetailScreen from '../screens/InvoiceDetailScreen';
@@ -160,6 +162,16 @@ const SettingsStack = () => (
       component={ErrorDashboardScreen}
       options={{ title: 'Error Dashboard', headerShown: true }}
     />
+    <Stack.Screen 
+      name="Import" 
+      component={ImportScreen} 
+      options={{ title: 'Import Subscriptions', headerShown: true }} 
+    />
+    <Stack.Screen 
+      name="Export" 
+      component={ExportScreen} 
+      options={{ title: 'Export Subscriptions', headerShown: true }} 
+    />
   </Stack.Navigator>
 );
 

src/navigation/types.ts

@@ -20,6 +20,8 @@ export type RootStackParamList = {
   LanguageSettings: undefined;
   SessionManagement: undefined;
   ErrorDashboard: undefined;
+  Import: undefined;
+  Export: undefined;
   SegmentManagement: undefined;
   SegmentDetail: { segmentId: string };
   Gamification: undefined;