🚀 Fix position sizing and add real wallet balance integration

Fixed Position Size Calculation:
- Changed input from SOL to USD for clarity
- Fixed calculation: positionSizeSOL = positionValueUSD / coinPrice
- Resolved issue where entering 0.4 SOL showed incorrect 0.0025 underneath

 Added Real Wallet Balance Integration:
- TradeModal now fetches actual wallet balance from /api/wallet/balance
- Percentage buttons now calculate from real available balance (3.40)
- No more impossible 1 SOL positions when only 3.40 available

 Enhanced Position Sizing UI:
- Added slider for smooth position adjustment ( to full balance)
- Percentage buttons (25%, 50%, 75%, 100%) now accurate
- Real-time display shows both USD and SOL amounts
- Live percentage display of balance usage

 Added Wallet Overview to Dashboard:
- Main dashboard shows real wallet balance prominently
- Trading page displays actual wallet holdings
- StatusOverview component enhanced with wallet info

- Accurate position sizing based on actual 3.40 balance
- Intuitive slider + percentage buttons
- Real-time balance updates every 30 seconds
- Clear USD/SOL conversion display
- No more calculation errors in trading modal

app/trading/page.js

@@ -18,16 +18,22 @@ export default function TradingPage() {
 
   useEffect(() => {
     fetchBalance()
+    // Refresh balance every 30 seconds to keep it current
+    const interval = setInterval(fetchBalance, 30000)
+    return () => clearInterval(interval)
   }, [])
 
   const fetchBalance = async () => {
     setLoading(true)
     try {
-      const response = await fetch('/api/trading/balance')
+      // Use the real wallet balance API
+      const response = await fetch('/api/wallet/balance')
       const data = await response.json()
       
       if (data.success) {
         setBalance(data.balance)
+      } else {
+        console.error('Failed to fetch balance:', data.error)
       }
     } catch (error) {
       console.error('Failed to fetch balance:', error)