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

.env

@@ -35,6 +35,8 @@ API_SECRET_KEY=2a344f0149442c857fb56c038c0c7d1b113883b830bec792c76f1e0efa15d6bb
 # Drift SDK REQUIRES WebSocket subscriptions - Alchemy doesn't support this
 # Alchemy "working" state was temporary - always breaks after first trade or shortly after init
 SOLANA_RPC_URL=https://mainnet.helius-rpc.com/?api-key=5e236449-f936-4af7-ae38-f15e2f1a3757
+# Alchemy RPC URL for trade operations (better sustained rate limits, optional)
+ALCHEMY_RPC_URL=https://solana-mainnet.g.alchemy.com/v2/fDKYNe7eL83HRH5Y4xW54qg6tTk0L7y0
 
 # Alternative RPC providers (reference):
 #