Map unmapped QuickBooks accounts automatically (#2642)

Fills only QuickBooks accounts with no current mapping (an existing mapping always wins), from the latest completed QuickBooks read, in order: system role (A/R, A/P, retained earnings, opening balance equity), connected bank/card last four digits, exact account number or name. For an established QuickBooks file (a transaction dated before the posting cutoff), also creates a Median account mirroring each remaining QuickBooks account, renames role-matched system accounts to the QuickBooks name, and deactivates unused Median accounts that have no QuickBooks counterpart. A new file (or no cutoff) gets matches only. Idempotent; nothing posts. The same run happens after every completed QuickBooks read.