fix: Increase transaction confirmation timeout to 60s for Alchemy Growth

- Alchemy Growth (10,000 CU/s) can handle longer confirmation waits
- Increased timeout from 30s to 60s in both openPosition() and closePosition()
- Added debug logging to execute endpoint to trace hang points
- Configured dual RPC: Alchemy primary (transactions), Helius fallback (subscriptions)
- Previous 30s timeout was causing premature failures during Solana congestion
- This should resolve 'Transaction was not confirmed in 30.00 seconds' errors

Related: User reported n8n webhook returning 500 with timeout error

.env

@@ -31,11 +31,15 @@ API_SECRET_KEY=2a344f0149442c857fb56c038c0c7d1b113883b830bec792c76f1e0efa15d6bb
 
 # Solana RPC URL (Required for blockchain access)
 # 
-# RECOMMENDED: Helius (best performance, free tier available)
-# Get free API key at: https://helius.dev
-SOLANA_RPC_URL=https://mainnet.helius-rpc.com/?api-key=5e236449-f936-4af7-ae38-f15e2f1a3757
+# PRIMARY: Alchemy Growth (10,000 CU/s, best for transactions)
+# Used for: Transaction submission and confirmation
+SOLANA_RPC_URL=https://solana-mainnet.g.alchemy.com/v2/5A0iA5UYpsmP9gkuezYeg
 
-# Alternative RPC providers (if not using Helius):
+# FALLBACK: Helius (for WebSocket subscriptions if needed)
+# Used for: Account subscriptions (Drift SDK initialization)
+SOLANA_FALLBACK_RPC_URL=https://mainnet.helius-rpc.com/?api-key=5e236449-f936-4af7-ae38-f15e2f1a3757
+
+# Alternative RPC providers (reference):
 # 
 # QuickNode: https://solana-mainnet.quiknode.pro/YOUR_ENDPOINT/
 # Alchemy: https://solana-mainnet.g.alchemy.com/v2/YOUR_ALCHEMY_KEY