feat(parties): phase 1 substrate, one party per counterpart (#2162)

* feat(parties): phase 1 substrate, one party per counterpart

Adds the identity layer above customers and suppliers, which keep their
tables and every foreign key and gain a nullable party_id.

- parties: company-scoped identity with status (suggested | confirmed),
  kind, alias keys, origin and merged_into. One live party per org number
  and company, enforced by a partial unique index; merged losers leave the
  index so a merge can be undone. This is the unique key the
  duplicate-invoice guard has lacked, since suppliers never had one.
- party_facts: statements with a source, a rank (preferred | normal |
  deprecated) and two time axes, never overwritten.
- party_identities: bankgiro, plusgiro, IBAN and friends per party, with
  seen and paid counts and a known | unverified status.
- party_decisions: every human action on a party as a labelled example.
- normalize_org_number(text): SQL mirror of lib/invariants/org-number.ts
  (strip separators, drop the century on 12 digits, Luhn check, 10 digits).
- ensure_party(): find by org number inside the company, else create.
  Name-only rows never merge at insert time; a name merge is a recorded
  human decision.
- Backfill: one party per existing supplier and customer, merged on org
  number, suppliers first so both roles land on one party.
- Archive contract: the four tables are master data in the full archive.

Observed parties (keys derived from voucher and bank text) are not stored;
they stay computed by the ledger-context RPC. No posted entry is touched.

Co-Authored-By: Claude Fable 5.1 <noreply@anthropic.com>

* fix(parties): tenant-safe composite foreign keys on every party link

Facts, identities, decisions, customers.party_id, suppliers.party_id and
parties.merged_into now reference parties(id, company_id), so a row can
only point at a party in its own company. ON DELETE SET NULL names
party_id so role rows keep their company_id. Adds a pg-real test that
rejects every cross-company link and checks company_id survives a party
delete.

Co-Authored-By: Claude Fable 5.1 <noreply@anthropic.com>

---------

Co-authored-by: Jakob Wennberg <311770904+jakobwennberg-oss@users.noreply.github.com>
Co-authored-by: Claude Fable 5.1 <noreply@anthropic.com>

lib/reports/full-archive-export.ts

@@ -967,6 +967,12 @@ export const MASTER_DATA_DUMP_TABLES: MasterDataTableSpec[] = [
   // Counterparties and articles
   { name: 'customers', file: 'customers.json', orderBy: 'created_at' },
   { name: 'suppliers', file: 'suppliers.json', orderBy: 'created_at' },
+  // The party layer above customers and suppliers: identities, facts with
+  // provenance, payment identities and the human decisions that shaped them.
+  { name: 'parties', file: 'parties.json', orderBy: 'created_at' },
+  { name: 'party_facts', file: 'party_facts.json', orderBy: 'recorded_at' },
+  { name: 'party_identities', file: 'party_identities.json', orderBy: 'created_at' },
+  { name: 'party_decisions', file: 'party_decisions.json', orderBy: 'created_at' },
   { name: 'articles', file: 'articles.json', orderBy: 'created_at' },
   // Customer invoicing
   { name: 'invoices', file: 'invoices.json', orderBy: 'invoice_date' },