Distinguish debit and credit postings sharing an upstream reference

internal/banking/import.go

@@ -18,7 +18,15 @@ func digest(parts ...string) string {
 	h := sha256.Sum256(b)
 	return hex.EncodeToString(h[:])
 }
-func identity(f domain.Facts) string { return digest(f.AccountID, f.Source, f.ExternalID) }
+func identity(f domain.Facts) string {
+	// Banks can reuse a reference for a debit and its credit counterpart.
+	// Facts are normalized before lookup; never rewrite stored journal IDs.
+	direction := "credit"
+	if strings.HasPrefix(string(f.Amount), "-") {
+		direction = "debit"
+	}
+	return digest(f.AccountID, f.Source, f.ExternalID, direction)
+}
 func fingerprint(f domain.Facts) string {
 	return digest(f.AccountID, f.BookingDate, f.ValueDate, f.Amount.String(), f.Currency, strings.Join(strings.Fields(f.RawDescription), " "), strings.ToLower(strings.Join(strings.Fields(f.Counterparty), " ")), f.CounterpartyIBAN)
 }
@@ -30,9 +38,10 @@ func sameBookedMoney(a, b domain.Facts) bool {
 }
 
 // NormalizeAndDedupe returns new records without mutating the input. Stable bank
-// entry references take precedence over text. CSV rows without references use
-// occurrence counts, not a set: two identical rows remain two transactions and
-// importing the same export again creates none. For overlapping partial exports,
+// entry references, scoped by account, source and debit/credit direction, take
+// precedence over text. Rows without references use occurrence counts, not a set:
+// two identical rows remain two transactions; reimporting creates none.
+// For overlapping partial exports,
 // indistinguishable rows cannot prove an additional occurrence; import complete
 // overlapping date windows to establish multiplicity.
 //