Integrate Polkadot.js blockchain with mobile wallet (FAZ 1)

This commit implements the complete blockchain integration for the mobile app's wallet functionality:

**Polkadot.js Integration:**
- Created PolkadotContext for mobile with full blockchain connectivity
- Implemented wallet creation with mnemonic seed phrases
- Added secure key management with AsyncStorage
- Connected to Pezkuwi testnet (wss://beta-rpc.pezkuwi.art)

**WalletScreen Enhancements:**
- Live blockchain balance fetching for HEZ (native token)
- Live balance fetching for PEZ and wUSDT (assets)
- Real-time balance updates every 30 seconds
- Actual send transactions using api.tx.balances.transfer (HEZ)
- Actual send transactions using api.tx.assets.transfer (PEZ, wUSDT)
- Transaction signing with user's keypair
- Loading states and error handling
- Wallet creation flow for new users
- Connect/disconnect wallet functionality

**Bottom Navigation:**
- Created BottomTabNavigator with 5 tabs
- Added WalletScreen with live blockchain integration
- Added BeCitizenScreen (citizenship application)
- Added ReferralScreen (referral program)
- Renamed SettingsScreen to ProfileScreen
- Custom center button for "Be Citizen" feature

**App Structure:**
- Wrapped app with PolkadotProvider in App.tsx
- Updated AppNavigator to use BottomTabNavigator
- Integrated language selection flow with blockchain features

All wallet features now use live blockchain data instead of mock data.

mobile/src/navigation/AppNavigator.tsx

@@ -9,15 +9,13 @@ import { KurdistanColors } from '../theme/colors';
 import WelcomeScreen from '../screens/WelcomeScreen';
 import SignInScreen from '../screens/SignInScreen';
 import SignUpScreen from '../screens/SignUpScreen';
-import DashboardScreen from '../screens/DashboardScreen';
-import SettingsScreen from '../screens/SettingsScreen';
+import BottomTabNavigator from './BottomTabNavigator';
 
 export type RootStackParamList = {
   Welcome: undefined;
   SignIn: undefined;
   SignUp: undefined;
-  Dashboard: undefined;
-  Settings: undefined;
+  MainApp: undefined;
 };
 
 const Stack = createStackNavigator<RootStackParamList>();
@@ -100,27 +98,8 @@ const AppNavigator: React.FC = () => {
             </Stack.Screen>
           </>
         ) : (
-          // Show main app if authenticated
-          <>
-            <Stack.Screen name="Dashboard">
-              {(props) => (
-                <DashboardScreen
-                  {...props}
-                  onNavigateToWallet={() => console.log('Navigate to Wallet')}
-                  onNavigateToSettings={() => props.navigation.navigate('Settings')}
-                />
-              )}
-            </Stack.Screen>
-            <Stack.Screen name="Settings">
-              {(props) => (
-                <SettingsScreen
-                  {...props}
-                  onBack={() => props.navigation.goBack()}
-                  onLogout={handleLogout}
-                />
-              )}
-            </Stack.Screen>
-          </>
+          // Show main app (bottom tabs) if authenticated
+          <Stack.Screen name="MainApp" component={BottomTabNavigator} />
         )}
       </Stack.Navigator>
     </NavigationContainer>