Reframe the implementation notes as design decisions (no code exists
yet) and resolve the open design questions:
- card: contract fuel card only; retail rows carry no card
- customer delete also guards against invoices and cards
- invoice: outgoing fuel only; add explicit send (draft -> sent);
--all fans out to one invoice per customer; document statuses
- VAT: amounts stored inclusive, 25% base/VAT split at invoice time
- file import: v1 = epsilon TSV only; one DB transaction per import;
batch-total mismatch aborts with exit code 1
- file export --format raw is source-faithful; raw errors elsewhere
- batch: document derived nature; update = manual reconciliation;
list gains --from/--to/--year filters
- daemon status is local-only (no external check); pidfile/logs under
a configured state directory
- db: --force on reset/restore; timestamped backups in configured dir;
status reports migration version
- add config show, --version, --config precedence, exit-code table,
business-key ID semantics, and status values
jakob