feat: Add wallet dashboard with balance and transfer functionality

New Components:
- AccountBalance: Real-time balance display with free/reserved breakdown
- TransferModal: Token transfer interface with transaction signing
- WalletDashboard: Complete wallet management page

Features:
- Live balance fetching from blockchain
- Balance subscription for real-time updates
- Transfer modal with recipient and amount input
- Transaction signing via Polkadot.js extension
- Transaction status tracking (signing, pending, success, error)
- Account switching support
- Responsive dashboard layout
- Quick action buttons (Send, Receive, History)

Technical:
- Integration with PolkadotContext
- web3FromAddress for transaction signing
- signAndSend for blockchain transactions
- Balance conversion (plancks to tokens)
- Error handling and user feedback
- Toast notifications for transaction status

Navigation:
- Added /wallet route with ProtectedRoute
- Added Wallet link to navigation menu

src/components/AppLayout.tsx

@@ -90,6 +90,13 @@ const AppLayout: React.FC = () => {
 
                     {t('nav.dashboard', 'Dashboard')}
                   </button>
+                  <button
+                    onClick={() => navigate('/wallet')}
+                    className="text-gray-300 hover:text-white transition-colors flex items-center gap-1"
+                  >
+                    <Wallet className="w-4 h-4" />
+                    {t('nav.wallet', 'Wallet')}
+                  </button>
                   <button 
                     onClick={() => navigate('/profile-settings')}
                     className="text-gray-300 hover:text-white transition-colors flex items-center gap-1"