feat(import): let the Fortnox import fetch older fiscal years: the three-year limit becomes a default selection (#2280)

* fix(import): say which fiscal years the Fortnox connection fetches, list the ones left out

Root cause: the guided provider migration fetches SIE only for fiscal years
that start within a rolling three-calendar-year window
(getAllowedFiscalYears in extensions/general/arcim-migration/lib/sie-fetcher.ts:
current year and the two before it). A first, broken year 2022/2023 starts
in 2022 and falls outside the window in 2026, and the wizard said nothing:
not before the import, not after. Users concluded the books were complete,
or that they had done something wrong (issue #2211, second report via
support 2026-08-27).

Fix:
- The fetcher already lists every fiscal year at the source before applying
  the window, so the left-out years are derived from that same list at no
  extra provider call: `omittedYears` (years starting before the window,
  oldest first, with the provider's own from/to dates so a broken year is
  named as "2022-09-01 till 2023-12-31"). Fortnox and Briox year refs now
  carry those bounds; WINT's listYears reports the unfiltered year list.
- GET /preview returns `fiscalYearWindow` and `omittedYears`; GET /sie-data
  returns `omittedYears` next to `failedYears`.
- Wizard, preview step (before the import runs): one muted sentence that the
  direct connection fetches the three latest fiscal years (years starting in
  {fromYear} or later); when years are left out, they are named with a link
  to the SIE import (one SIE file per year under Import, oldest first).
- Wizard, result step: a "Räkenskapsår som inte följde med" section naming
  the omitted years with the same SIE pointer, shown when SIE data was
  imported in the run.
- MCP: the connect_migration tool description, its instructions and the
  onboarding skill claimed the wizard "fetches every fiscal year"; they now
  say three latest, older years via SIE.
- Strings in both messages/sv.json and messages/en.json.

Out of scope: fetching more years through the connection (#2238).

Co-Authored-By: Claude Fable 5.1 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_015qgLgdt4mLmha1ZLFMwq1u

* feat(import): make the Fortnox import's three-year limit a default selection, not a cap

Root cause, from first principles: the guided provider migration fetched
SIE only for fiscal years starting within a rolling three-calendar-year
window (getAllowedFiscalYears in
extensions/general/arcim-migration/lib/sie-fetcher.ts, introduced in #718
with no stated reason). The window was a silent cap: the wizard never said
it existed, and a first broken year 2022/2023 simply never arrived
(#2211). The user's actual problem is that the year is missing from the
books, so explaining the cap (the previous commit) treats the symptom.

What the window gated, by evidence: only the SIE fetch. Documents already
list every Fortnox financial year and match against the vouchers that
exist locally (import-documents.ts), invoices, customers, suppliers and
assets are not year-gated, and the SIE import itself is one request per
year (hosted function limit 300 s, import_sie_journal_entries
statement_timeout 290 s), so its cost is linear in wall time and bounded
per year regardless of how many years are imported. The only place the
number of years multiplies inside one invocation is /preview and
/sie-data: one SIE export per year (Fortnox client: 15 s per-call timeout,
3 attempts, backoff up to 30 s, 4 req/s) fetched and parsed inside a
single 300 s function, and /sie-data returns every raw file in one
response. The repo holds no measurement of Fortnox's per-year SIE export
latency, and the maintainer's memory is that a full history can take
unreasonably long, so a fixed lift to every year cannot be shown safe for
a long history.

Fix: the window becomes the DEFAULT selection, and the user chooses.
- sie-fetcher: fetchProviderSieFiles takes `years` (explicit start years);
  without it the default window applies. The result carries `sourceYears`
  (every year at the source, oldest first, with the provider's own bounds
  and an inDefaultSelection flag) and `omittedYears` (source years outside
  the selection). Both derived from the year list already fetched: no
  extra provider call. Fortnox and Briox year refs carry their bounds;
  WINT's listYears reports the unfiltered list and its voucher chain
  follows the selection.
- GET /preview returns `sourceYears`; GET /sie-data honours `?years=`
  (validated, deduplicated, oldest first; 400 VALIDATION_ERROR when
  malformed) and returns `omittedYears`. PROVIDER_SIE_NO_YEARS names the
  selection.
- Wizard, preview step: a "Räkenskapsår att hämta" picker with one
  checkbox row per source year, the three latest ticked by default, older
  years marked "tar längre tid"; Fortsätt is disabled with an attn line
  until at least one year is ticked. The selection is sent to /sie-data,
  so each extra year is the user's own wait, and it fails loudly there,
  before any ledger write, if it is too much.
- Wizard, result step: the per-year lines already report exactly what was
  imported; a "Räkenskapsår som inte hämtades" section names the source
  years outside the selection, with the re-run path (documents come
  along) and the SIE path.
- MCP connect_migration description, instructions and the onboarding skill
  say "three latest by default, older years selectable" instead of "every
  fiscal year".
- Strings in both messages/sv.json and messages/en.json.

Closes #2238 as well: the wish to fetch more years is the same control.

Co-Authored-By: Claude Fable 5.1 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_015qgLgdt4mLmha1ZLFMwq1u

* fix(import): bound the fiscal-year selection per import run

Superagent P2 on #2280: the `years` selection was unbounded and every
selected year is one provider export fetched and parsed inside the single
300 s /sie-data invocation, so nothing bounded the work before provider
calls.

The bound: MAX_SELECTED_FISCAL_YEARS = 6, exported from sie-fetcher.ts with
the derivation. One export call is 15 s per attempt (Fortnox client
FETCH_TIMEOUT_MS), 3 attempts with 1 s and 2 s backoff (retry defaults),
so a year that times out on every attempt costs 48 s; six such years are
288 s, leaving 12 s of the 300 s hosted function for the year listing,
parsing and the response; seven would be 336 s.

Enforced server-side:
- /sie-data refuses a selection of more than the cap with 400
  VALIDATION_ERROR naming the cap, before the consent is resolved, so an
  oversized request does no provider work.
- fetchProviderSieFiles throws FiscalYearSelectionError for a selected year
  the source does not have, right after the year listing and before any
  export; /sie-data maps it to 400 VALIDATION_ERROR naming the year.
- /preview returns maxSelectedYears so the picker enforces the same number
  without a client-side copy: Fortsätt is disabled and an attn line says how
  many can be fetched at once and that older years go in a second run
  (sv + en).

Tests: cap accepted at 6 and refused at 7 with no provider call, unknown
year refused (route and fetcher), the cap's arithmetic, maxSelectedYears
on /preview.

Co-Authored-By: Claude Fable 5.1 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_015qgLgdt4mLmha1ZLFMwq1u

---------

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

messages/en.json

@@ -5627,6 +5627,15 @@
     "ext_arcim_documents_provider_message": "Source system response: {message}",
     "ext_arcim_option_series_help": "Vouchers keep their series from the source system (A, D, E ...). The series here is only used for vouchers without one.",
     "ext_arcim_option_sie_required_hint": "The ledger (chart of accounts, opening balances and verifications) has not been imported yet. Tick Bokföringsdata (SIE) to fetch it in the same run: customers, suppliers and invoices cannot be imported without it.",
+    "ext_arcim_year_select_kicker": "Fiscal years to fetch",
+    "ext_arcim_year_select_lede": "The three most recent fiscal years are selected by default. Tick older years to fetch them too: it takes longer, and attached documents come along.",
+    "ext_arcim_year_select_older": "takes longer",
+    "ext_arcim_year_select_none": "Select at least one fiscal year.",
+    "ext_arcim_year_select_too_many": "At most {max} fiscal years can be fetched at once. Older years can be fetched in a second run.",
+    "ext_arcim_omitted_years_kicker": "Fiscal years not fetched",
+    "ext_arcim_omitted_years_result": "{count, plural, one {Not selected in this run. Run a new migration with it ticked to fetch that year too (attached documents come along), or upload it as a SIE file under Import.} other {Not selected in this run. Run a new migration with them ticked to fetch those years too (attached documents come along), or upload them as one SIE file per year under Import, oldest first.}}",
+    "ext_arcim_omitted_years_sie_link": "Go to the SIE import",
+    "ext_arcim_fiscal_year_span": "{from} to {to}",
     "ext_arcim_documents_result_description": "The document import is complete.",
     "ext_arcim_documents_imported": "Imported",
     "ext_arcim_documents_skipped": "Already present",

messages/sv.json

@@ -5627,6 +5627,15 @@
     "ext_arcim_documents_provider_message": "Svar från källsystemet: {message}",
     "ext_arcim_option_series_help": "Verifikat behåller sin serie från källsystemet (A, D, E ...). Serien här används bara för verifikat som saknar serie.",
     "ext_arcim_option_sie_required_hint": "Bokföringen (kontoplan, ingående balanser och verifikationer) har inte importerats än. Kryssa i Bokföringsdata (SIE) för att hämta den i samma körning: kunder, leverantörer och fakturor kan inte importeras utan den.",
+    "ext_arcim_year_select_kicker": "Räkenskapsår att hämta",
+    "ext_arcim_year_select_lede": "De tre senaste räkenskapsåren är förvalda. Bocka i äldre år för att hämta dem också: det tar längre tid, och kopplade underlag följer med.",
+    "ext_arcim_year_select_older": "tar längre tid",
+    "ext_arcim_year_select_none": "Välj minst ett räkenskapsår.",
+    "ext_arcim_year_select_too_many": "Högst {max} räkenskapsår kan hämtas åt gången. Äldre år kan hämtas i en ny körning.",
+    "ext_arcim_omitted_years_kicker": "Räkenskapsår som inte hämtades",
+    "ext_arcim_omitted_years_result": "{count, plural, one {Inte valt i den här körningen. Kör en ny migrering och bocka i det för att hämta även det året (kopplade underlag följer med), eller ladda upp det som en SIE-fil under Import.} other {Inte valda i den här körningen. Kör en ny migrering och bocka i dem för att hämta även de åren (kopplade underlag följer med), eller ladda upp dem som en SIE-fil per år under Import, äldsta året först.}}",
+    "ext_arcim_omitted_years_sie_link": "Gå till SIE-importen",
+    "ext_arcim_fiscal_year_span": "{from} till {to}",
     "ext_arcim_documents_result_description": "Underlagsimporten är klar.",
     "ext_arcim_documents_imported": "Importerade",
     "ext_arcim_documents_skipped": "Fanns redan",