feat: Hybrid RPC strategy - Helius for init, Alchemy for trades

CRITICAL FIX: Rate limiting causing unprotected positions

Root Cause:
- Rate limit errors preventing exit order placement after opening positions
- Positions opened with NO on-chain TP/SL protection
- If container crashes, position has unlimited risk exposure

Hybrid RPC Solution:
- Helius RPC: Drift SDK initialization (handles burst subscriptions perfectly)
- Alchemy RPC: Trade operations - open, close, confirmations (better sustained rate limits)
- Graceful fallback: If Alchemy not configured, uses Helius for everything

Implementation:
- DriftService: Dual connections (connection + tradeConnection)
- getTradeConnection() returns Alchemy if configured, else Helius
- openPosition() and closePosition() use tradeConnection for confirmTransaction()
- Added ALCHEMY_RPC_URL to .env (optional)

Configuration:
- SOLANA_RPC_URL: Helius (existing)
- ALCHEMY_RPC_URL: Added with your Alchemy key

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

Logs show: '🔀 Hybrid RPC mode: Helius for init, Alchemy for trades'

Next: Test with new trade to verify orders place successfully

lib/drift/client.ts

@@ -444,13 +444,6 @@ export class DriftService {
     return this.driftClient!
   }
 
-  /**
-   * Get Solana connection instance
-   */
-  getConnection(): Connection {
-    return this.connection
-  }
-
   /**
    * Get user instance
    */