feat(mobile): implement DEX/Swap interface with real-time blockchain integration

PHASE 1 - Feature 1: DEX/Swap (COMPLETED ✅)

## New Components (5 files - 550 lines):
1. TokenIcon.tsx - Token emoji icons component
2. AddressDisplay.tsx - Formatted address display with copy functionality
3. BalanceCard.tsx - Token balance card with change indicators
4. TokenSelector.tsx - Modal token selector with search
5. Updated components/index.ts - Export new components

## New Screen:
SwapScreen.tsx (800 lines) - Full-featured DEX swap interface

## Features Implemented:
✅ Real-time blockchain integration via Polkadot.js
✅ Live balance fetching for all tokens (HEZ, wHEZ, PEZ, wUSDT)
✅ Pool reserve queries from assetConversion pallet
✅ Automatic price calculations using shared DEX utilities
✅ Price impact calculation and display
✅ Slippage tolerance settings (0.5% to 50%)
✅ Minimum received amount calculation
✅ Transaction fee display (0.3%)
✅ Transaction signing and sending
✅ Success/error handling with user-friendly messages
✅ Loading states throughout
✅ Token balance display for all available tokens
✅ Swap token positions functionality
✅ Settings modal for slippage configuration
✅ Preset slippage buttons (0.5%, 1%, 2%, 5%)

## Blockchain Integration:
- Uses shared/utils/dex.ts utilities (formatTokenBalance, parseTokenInput, calculatePriceImpact, getAmountOut, calculateMinAmount)
- Real-time pool reserve fetching from chain
- Transaction execution via assetConversion.swapTokensForExactTokens
- Proper error extraction from dispatchError
- Event monitoring for transaction finalization

## UI/UX:
- Kurdistan color palette (green, red, yellow)
- Price impact color coding (green<1%, yellow 1-3%, red>3%)
- Disabled states for invalid inputs
- Modal-based settings interface
- Responsive layout with ScrollView
- Proper keyboard handling (keyboardShouldPersistTaps)

## Navigation:
- Added Swap tab to BottomTabNavigator
- Swap icon: 🔄 (focused) / ↔️ (unfocused)
- Positioned between Wallet and BeCitizen tabs

## Security:
- Keypair loaded from secure storage
- No private keys in state
- Proper transaction validation
- Slippage protection

## Dependencies:
- Uses existing Polkadot.js API (16.5.2)
- No new dependencies added
- Fully compatible with existing infrastructure

## Testing Checklist:
- [ ] Test on iOS simulator
- [ ] Test on Android emulator
- [ ] Test with real blockchain (beta testnet)
- [ ] Test swap HEZ → PEZ
- [ ] Test swap PEZ → wUSDT
- [ ] Test slippage settings
- [ ] Test error handling (insufficient balance)
- [ ] Test loading states
- [ ] Test token selector

## Next Steps:
- Implement P2P Fiat Trading (Phase 1, Feature 2)
- Add transaction history for swaps
- Implement swap analytics

Estimated completion: +10% (50% → 60%)

mobile/src/components/AddressDisplay.tsx

@@ -0,0 +1,94 @@
+import React, { useState } from 'react';
+import {
+  View,
+  Text,
+  TouchableOpacity,
+  StyleSheet,
+  Clipboard,
+} from 'react-native';
+import { KurdistanColors } from '../theme/colors';
+
+interface AddressDisplayProps {
+  address: string;
+  label?: string;
+  copyable?: boolean;
+}
+
+/**
+ * Format address for display (e.g., "5GrwV...xQjz")
+ */
+const formatAddress = (address: string): string => {
+  if (!address) return '';
+  return `${address.slice(0, 6)}...${address.slice(-4)}`;
+};
+
+export const AddressDisplay: React.FC<AddressDisplayProps> = ({
+  address,
+  label,
+  copyable = true,
+}) => {
+  const [copied, setCopied] = useState(false);
+
+  const handleCopy = () => {
+    if (!copyable) return;
+
+    Clipboard.setString(address);
+    setCopied(true);
+    setTimeout(() => setCopied(false), 2000);
+  };
+
+  return (
+    <View style={styles.container}>
+      {label && <Text style={styles.label}>{label}</Text>}
+      <TouchableOpacity
+        onPress={handleCopy}
+        disabled={!copyable}
+        activeOpacity={0.7}
+      >
+        <View style={styles.addressContainer}>
+          <Text style={styles.address}>{formatAddress(address)}</Text>
+          {copyable && (
+            <Text style={styles.copyIcon}>{copied ? '✅' : '📋'}</Text>
+          )}
+        </View>
+      </TouchableOpacity>
+      {copied && <Text style={styles.copiedText}>Copied!</Text>}
+    </View>
+  );
+};
+
+const styles = StyleSheet.create({
+  container: {
+    marginVertical: 4,
+  },
+  label: {
+    fontSize: 12,
+    color: '#666',
+    marginBottom: 4,
+  },
+  addressContainer: {
+    flexDirection: 'row',
+    alignItems: 'center',
+    padding: 8,
+    backgroundColor: '#F5F5F5',
+    borderRadius: 8,
+    borderWidth: 1,
+    borderColor: '#E0E0E0',
+  },
+  address: {
+    flex: 1,
+    fontSize: 14,
+    fontFamily: 'monospace',
+    color: '#000',
+  },
+  copyIcon: {
+    fontSize: 18,
+    marginLeft: 8,
+  },
+  copiedText: {
+    fontSize: 12,
+    color: KurdistanColors.kesk,
+    marginTop: 4,
+    textAlign: 'center',
+  },
+});