feat: Hybrid RPC strategy (Helius init + Alchemy trades)

CRITICAL: Fix rate limiting by using dual RPC approach

Problem:
- Helius RPC gets overwhelmed during trade execution (429 errors)
- Exit orders fail to place, leaving positions UNPROTECTED
- No on-chain TP/SL orders = unlimited risk if container crashes

Solution: Hybrid RPC Strategy
- Helius for Drift SDK initialization (handles burst subscriptions well)
- Alchemy for trade operations (better sustained rate limits)
- Falls back to Helius if Alchemy not configured

Implementation:
- DriftService now has two connections: connection (Helius) + tradeConnection (Alchemy)
- Added getTradeConnection() method for trade operations
- Updated openPosition() and closePosition() to use trade connection
- Added ALCHEMY_RPC_URL to .env (optional, falls back to Helius)

Benefits:
- Helius: 0 subscription errors during init (proven reliable for SDK setup)
- Alchemy: 300M compute units/month for sustained trade operations
- Best of both worlds: reliable init + reliable trades

Files:
- lib/drift/client.ts: Dual connection support
- lib/drift/orders.ts: Use getTradeConnection() for confirmations
- .env: Added ALCHEMY_RPC_URL

Testing: Deploy and execute test trade to verify orders place successfully

lib/drift/orders.ts

@@ -147,7 +147,7 @@ export async function openPosition(
     
     // CRITICAL: Confirm transaction actually executed on-chain
     console.log('⏳ Confirming transaction on-chain...')
-    const connection = driftService.getConnection()
+    const connection = driftService.getTradeConnection() // Use Alchemy for trade operations
     
     try {
       const confirmation = await connection.confirmTransaction(txSig, 'confirmed')
@@ -559,7 +559,7 @@ export async function closePosition(
     // CRITICAL: Confirm transaction on-chain to prevent phantom closes
     // BUT: Use timeout to prevent API hangs during network congestion
     console.log('⏳ Confirming transaction on-chain (30s timeout)...')
-    const connection = driftService.getConnection()
+    const connection = driftService.getTradeConnection() // Use Alchemy for trade operations
     
     try {
       const confirmationPromise = connection.confirmTransaction(txSig, 'confirmed')