fix(import): raise statement_timeout on import_sie_journal_entries to 290s (#1101)

A production Fortnox migration failed with "SIE-verifikationer kunde
inte importeras atomiskt: canceling statement due to statement
timeout": the atomic import RPC (20260712150000) inherits the 8s
authenticator statement_timeout, so any real-world multi-year SIE file
exceeds it and the whole import is cancelled and rolled back. Same
failure class as 20260629160100 (replace_sie_import / undo_sie_import);
same fix, a function-scoped statement_timeout of 290s sitting under the
calling routes' maxDuration = 300 ceiling.

Migration 20260721144311 is already applied to prod (proconfig verified
carrying statement_timeout=290s); the committed file is byte-identical
under the same version. The new pg-real ratchet pins the config on all
three SIE RPCs because CREATE OR REPLACE FUNCTION silently drops
ALTER FUNCTION settings.

Co-authored-by: Claude Fable 5 <noreply@anthropic.com>

supabase/migrations/20260721144311_import_sie_statement_timeout.sql

@@ -0,0 +1,22 @@
+-- Raise statement_timeout inside the atomic SIE import RPC so a large
+-- Fortnox/provider migration is not cancelled mid-import.
+--
+-- Same failure class and fix as 20260629160100 (replace_sie_import /
+-- undo_sie_import): a PostgREST request runs under the authenticator
+-- role's 8s statement_timeout, and import_sie_journal_entries commits an
+-- entire SIE file in one call (per-voucher loop, per-line inserts, audit
+-- triggers). A real-world multi-year migration (thousands of vouchers)
+-- exceeds 8s, the statement is cancelled ("canceling statement due to
+-- statement timeout"), and the whole import rolls back with
+-- "SIE-verifikationer kunde inte importeras atomiskt".
+--
+-- A function-scoped SET re-arms the timer for the duration of the call and
+-- is restored on exit. 290s sits just under the calling routes' maxDuration
+-- = 300 ceiling (/api/extensions/ext/[...path], /api/import/sie/execute,
+-- /api/v1/.../imports/sie), so the serverless layer stays the effective
+-- bound. Function body is unchanged; only configuration is altered.
+
+ALTER FUNCTION public.import_sie_journal_entries(uuid, uuid, uuid, jsonb)
+  SET statement_timeout = '290s';
+
+NOTIFY pgrst, 'reload schema';