DxFeed sync: trades load again with correct PnL

DxFeed sync now talks to the correct history server for your prop firm, which fixes cases where sync ran but returned no trades even though you had closed positions.

When your session expires, the connection is marked Expired and sync prompts you to Reconnect instead of failing quietly. Imported trades now store gross PnL in the trade row and derive commission from the difference between gross and net, so fees are not counted twice in your dashboard totals.

Sync also explains when DxFeed only returns open positions—those are skipped until you close the trade on your platform and sync again.