Reconcile account type/sub-type in QBO + CSV imports

Closes the remaining type/sub-type-consistency vector (create/edit + IIF
were already covered). The sign convention keys off sub-type, so a
mismatched pair posts with the wrong debit/credit sign.

- New AccountClassification.DefaultSubTypeForType(type).
- QBO import: QBO Type is reliable but DetailType frequently isn't
  mappable and fell back to AccountSubType.Other (an expense-range sub-type)
  — so an unmapped Liability/Equity/Revenue account would have posted
  debit-normal. Now reconciles the sub-type to the type when they disagree.
- CSV import: type and sub-type came from independent columns; now derives
  the type from the sub-type (sub-type authoritative, matching create/edit).
- IIF import already returns consistent (type, sub-type) tuples — unchanged.

Build clean; 293 unit tests pass.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

src/PowderCoating.Infrastructure/Services/CsvImportService.cs

@@ -2866,6 +2866,10 @@ public class CsvImportService : ICsvImportService
                         continue;
                     }
 
+                    // Sub-type is authoritative (matches account create/edit): derive the parent type
+                    // from it so a mismatched CSV pair can't post with the wrong debit/credit sign.
+                    accountType = AccountClassification.TypeForSubType(accountSubType);
+
                     DateTime? openingBalanceDate = null;
                     if (!string.IsNullOrWhiteSpace(record.OpeningBalanceDate)
                         && DateTime.TryParse(record.OpeningBalanceDate, out var parsedDate))