feat(periods): undo klarmarkera so an externally closed year can be reopened (#1978)

markPeriodClosedExternally ("klarmarkera") closes and locks an imported
year without a closing entry, and nothing could reverse it: unlockPeriod
refuses closed periods and the SIE replace flow refuses closed or locked
years. An owner who klarmarkerade five imported years and then found the
prior-year SIE file was wrong had no way back (Forsslund Systems,
2026-08-27).

reopenExternallyClosedPeriod reverses the mark while the closed state still
comes from klarmarkera (closed_externally set, no closing entry), clears the
lock, writes the audit_log row, and emits period.unlocked. New route
POST /api/bookkeeping/fiscal-periods/[id]/reopen-external with envelope codes
PERIOD_REOPEN_NOT_CLOSED / PERIOD_REOPEN_NOT_EXTERNAL; "Öppna igen" action
and "Avslutat i tidigare program" chip in Settings > Bookkeeping > Fiscal
years; unlock and SIE replace refusals now point at that path.

Co-authored-by: Jakob Wennberg <311770904+jakobwennberg-oss@users.noreply.github.com>
Co-authored-by: Claude Fable 5 <noreply@anthropic.com>

messages/en.json

@@ -1969,6 +1969,11 @@
     "fy_lock_success": "Fiscal year locked",
     "fy_unlock_success": "Fiscal year unlocked",
     "fy_action_error": "The action could not be completed",
+    "fy_status_closed_external": "Closed in previous system",
+    "fy_action_reopen": "Reopen",
+    "fy_reopen_confirm_title": "Reopen fiscal year?",
+    "fy_reopen_confirm_body": "{name} was marked as closed in a previous bookkeeping system. The mark is removed and the year is opened and unlocked so you can replace the SIE import or post additions. Mark it as closed again when you are done. This action is recorded in the audit log.",
+    "fy_reopen_success": "Fiscal year reopened",
     "fy_action_reset": "Reset",
     "fy_reset_dialog_title": "Reset fiscal year {name}?",
     "fy_reset_dialog_description": "All vouchers in the fiscal year are permanently deleted, regardless of how they were created. Documents are never deleted, only detached. Invoices, payments and bank transactions that were linked to the vouchers become unbooked and need to be booked again. This cannot be undone and is recorded in the audit log.",

messages/sv.json

@@ -1969,6 +1969,11 @@
     "fy_lock_success": "Räkenskapsåret är låst",
     "fy_unlock_success": "Räkenskapsåret är upplåst",
     "fy_action_error": "Åtgärden kunde inte slutföras",
+    "fy_status_closed_external": "Avslutat i tidigare program",
+    "fy_action_reopen": "Öppna igen",
+    "fy_reopen_confirm_title": "Öppna räkenskapsåret igen?",
+    "fy_reopen_confirm_body": "{name} markerades som avslutat i ett tidigare bokföringsprogram. Markeringen tas bort och året öppnas och låses upp, så att du kan ersätta SIE-importen eller bokföra kompletteringar. Klarmarkera året igen när du är klar. Åtgärden loggas i behandlingshistoriken.",
+    "fy_reopen_success": "Räkenskapsåret är öppet igen",
     "fy_action_reset": "Nollställ",
     "fy_reset_dialog_title": "Nollställ räkenskapsåret {name}?",
     "fy_reset_dialog_description": "Alla verifikat i räkenskapsåret raderas permanent, oavsett hur de skapades. Underlag och dokument raderas aldrig, de kopplas bara loss. Fakturor, betalningar och banktransaktioner som var kopplade till verifikaten blir obokförda och behöver bokföras om. Åtgärden kan inte ångras och loggas i behandlingshistoriken.",