revert: Remove Alchemy fallback causing crashes

- getFallbackConnection() code was causing execute endpoint to crash
- Reverting to Helius-only configuration
- Need to investigate root cause before re-adding fallback

lib/drift/client.ts

@@ -470,13 +470,6 @@ export class DriftService {
     return this.connection
   }
 
-  /**
-   * Get fallback connection (Alchemy for trade execution)
-   */
-  getFallbackConnection(): Connection | null {
-    return this.fallbackConnection || null
-  }
-
   /**
    * Get user instance
    */

lib/drift/orders.ts

@@ -146,16 +146,8 @@ export async function openPosition(
     console.log(`📝 Transaction submitted: ${txSig}`)
     
     // CRITICAL: Confirm transaction actually executed on-chain
-    // Use Alchemy (fallback RPC) for confirmation - higher throughput
-    console.log('⏳ Confirming transaction on-chain (using Alchemy for high throughput)...')
-    const alchemyConnection = driftService.getFallbackConnection()
-    const connection = alchemyConnection || driftService.getConnection()
-    
-    if (alchemyConnection) {
-      console.log('✅ Using Alchemy RPC for transaction confirmation')
-    } else {
-      console.log('⚠️ No fallback RPC available, using primary RPC')
-    }
+    console.log('⏳ Confirming transaction on-chain...')
+    const connection = driftService.getConnection()
     
     try {
       const confirmation = await connection.confirmTransaction(txSig, 'confirmed')
@@ -565,16 +557,9 @@ export async function closePosition(
     console.log(`✅ Close order placed! Transaction: ${txSig}`)
     
     // CRITICAL: Confirm transaction on-chain to prevent phantom closes
-    // Use Alchemy (fallback RPC) for confirmation - higher throughput
-    console.log('⏳ Confirming transaction on-chain (using Alchemy, 30s timeout)...')
-    const alchemyConnection = driftService.getFallbackConnection()
-    const connection = alchemyConnection || driftService.getConnection()
-    
-    if (alchemyConnection) {
-      console.log('✅ Using Alchemy RPC for transaction confirmation')
-    } else {
-      console.log('⚠️ No fallback RPC available, using primary RPC')
-    }
+    // BUT: Use timeout to prevent API hangs during network congestion
+    console.log('⏳ Confirming transaction on-chain (30s timeout)...')
+    const connection = driftService.getConnection()
     
     try {
       const confirmationPromise = connection.confirmTransaction(txSig, 'confirmed')