docs: add Docker cleanup instructions to prevent disk full issues

- Document build cache accumulation problem (40-50 GB typical)
- Add cleanup commands: image prune, builder prune, volume prune
- Recommend running after each deployment or weekly
- Typical space freed: 40-55 GB per cleanup
- Clarify what's safe vs not safe to delete
- Part of maintaining healthy development environment

lib/startup/init-position-manager.ts

@@ -109,7 +109,7 @@ async function validateOpenTrades() {
         }
         
         // Position EXISTS on Drift
-        const driftDirection = position.direction.toLowerCase() as 'long' | 'short'
+        const driftDirection = position.side.toLowerCase() as 'long' | 'short'
         
         if (driftDirection !== trade.direction) {
           console.log(`⚠️ DIRECTION MISMATCH: ${trade.symbol} DB=${trade.direction} Drift=${driftDirection}`)