Add Phase 19 bank accounting and reconciliation workflow

app/modules/accounting/bank_service.py

@@ -293,6 +293,19 @@ def _ensure_reviewed(tx):
     if tx.posting_status == "posted":
         raise ValueError("This bank transaction is already posted.")
 
+    # Phase 19: reconciliation is a duplicate-safety control. Rows already
+    # matched/probably matched to Tally must not be posted as new vouchers.
+    if getattr(tx, "reconciliation_status", "not_tested") in {
+        "matched",
+        "probable_match",
+        "duplicate_candidate",
+    }:
+        raise ValueError(
+            "Bank Reconciliation indicates that this transaction already has, "
+            "or probably has, a corresponding Tally voucher. Resolve the "
+            "reconciliation item instead of posting a duplicate entry."
+        )
+
 
 def queue_preflight(db, *, tx_id, tenant_id, client_id, workstation_id, user_id):
     tx = db.get(AccountingBankTransaction, tx_id)