Closes the test gaps from the PR #622 work + the export-scope feature:
- export scope: scopeLedger/normalizeScope (exported via _internal) unit tests +
renderTaxReportCsv income/cost/all output assertions (income drops supplier
rows, cost drops invoice rows, filename gets the scope tag).
- isUniqueViolation: Postgres 23505 / SQLITE_CONSTRAINT / "UNIQUE constraint
failed" message, false for FK + nullish (the IMAP claim-first race detector).
- getRenderedPagePath: out-of-range pages reject with PAGE_OUT_OF_RANGE before
touching pdftoppm/disk (the per-file resource bound).
Luca