Bug/customer invoice bug (#628)

* fix(supplier-invoices): self-assess reverse-charge VAT + link payments to vouchers

Reverse-charge supplier invoices now carry a per-item reverse_charge_rate (0.06/0.12/0.25). Under omvänd skattskyldighet the supplier charges 0% VAT, so the line vat_rate stays 0 and the buyer self-assesses fiktiv moms at the statutory rate. Centralizes rate resolution (resolveReverseChargeRate) and the ruta 20-24 basis-account guard (isReverseChargeBasisAccount) in vat-entries so the booking engine and review-dialog preview can no longer drift.

Adds the link_supplier_invoice_voucher pending operation: mark a leverantorsfaktura paid by linking an existing posted verifikat that debits 2440, with no new journal entry. Exposes find-candidates/link MCP tools and the bulk-reconcile helper, scoped under suppliers:read/write.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

* fix(vat): report yearly VAT over the rakenskapsar, not the calendar year

Annual VAT (helarsmoms) is filed per beskattningsar/rakenskapsar (SFL 26 kap), which can be extended or shortened up to 18 months. The previous Jan-Dec calendar span silently dropped part of an extended first year. calculateVatDeclaration now accepts a fiscalPeriodId and resolves the period's actual bounds for yearly; monthly/quarterly stay calendar. The reports UI passes the selected fiscal period, defaults the periodicity from the company's moms_period setting, and carries the period into the ruta drill-down. full-archive export threads the period id through too.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

* fix(migration): resolve supplier invoice status from payment amounts

The provider's lifecycle status and its payment status are computed independently upstream and can contradict each other (e.g. a Fortnox invoice marked booked but fully paid). Both the arcim entity-mapper and the Fortnox mapper now let payment state win: fully paid -> paid, partial -> partially_paid, otherwise the mapped lifecycle status, with credit notes forced terminal. Balance is compared numerically (never strict === 0) so float drift or a residual ore resolves cleanly, and an absent Balance is treated as unpaid.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

* fix(enable-banking): only ingest booked transactions to stop re-import drift

Pending entries are skipped during sync: a pending row is unstable across syncs (a later 'synka nu' returns it still pending or finally booked, often with a different effective date). Because both the dedup external_id and the content-dedup key are date-derived, that drift minted a new id and re-imported a transaction that already existed - observed in production as the same amount+description landing twice with different dates. Gating the import set on a stable booking_date removes the drift at the source and leaves booked rows' ids byte-identical.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

* chore(gitignore): ignore local SIE test fixtures

tests/fixtures/sie/ may contain real or scrubbed company data and must never be committed.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

* fix(invoice): handle errors during registration journal entry creation and ensure invoice rollback
feat(tests): add test for reverse charge rate handling on supplier invoice line items
feat(fortnox): ensure paid status reflects zero balance for fully paid invoices
chore(migrations): add reverse_charge_rate to supplier_invoice_items and backfill link_supplier_invoice_voucher

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Co-authored-by: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

messages/en.json

@@ -2489,9 +2489,8 @@
   },
   "supplier_invoice_editor": {
     "page_title": "Register supplier invoice",
-    "no_period_warning": "Invoice date {date} falls outside every fiscal year you have set up.",
-    "no_period_help": "Create the fiscal year so the invoice can be booked — otherwise it can't be registered.",
-    "create_period": "Create fiscal year",
+    "no_period_warning": "You're creating a supplier invoice for a fiscal year that doesn't exist ({date}).",
+    "no_period_help": "Create the fiscal year first, or change the invoice date — the invoice can't be registered without one.",
     "back_aria": "Back to supplier invoices",
     "back_aria_inbox": "Back to the inbox",
     "loading_inbox": "Loading data from inbox…",
@@ -2531,6 +2530,8 @@
     "col_amount": "Amount",
     "col_vat_rate": "VAT rate",
     "col_vat": "VAT",
+    "col_rc_vat_rate": "VAT rate (RC)",
+    "col_rc_vat": "Self-assessed VAT",
     "col_debit": "Debit",
     "col_credit": "Credit",
     "vat_rate_presets_aria": "Pick VAT rate from list",

messages/sv.json

@@ -2489,9 +2489,8 @@
   },
   "supplier_invoice_editor": {
     "page_title": "Registrera leverantörsfaktura",
-    "no_period_warning": "Fakturadatumet {date} ligger utanför alla upplagda räkenskapsår.",
-    "no_period_help": "Lägg upp räkenskapsåret så att fakturan kan bokföras – annars kan den inte registreras.",
-    "create_period": "Skapa räkenskapsår",
+    "no_period_warning": "Du skapar en leverantörsfaktura för ett räkenskapsår som inte finns ({date}).",
+    "no_period_help": "Lägg upp räkenskapsåret först, eller ändra fakturadatumet – fakturan kan inte registreras utan ett räkenskapsår.",
     "back_aria": "Tillbaka till leverantörsfakturor",
     "back_aria_inbox": "Tillbaka till inkorgen",
     "loading_inbox": "Laddar uppgifter från inkorgen…",
@@ -2531,6 +2530,8 @@
     "col_amount": "Belopp",
     "col_vat_rate": "Momssats",
     "col_vat": "Moms",
+    "col_rc_vat_rate": "Momssats (omvänd)",
+    "col_rc_vat": "Beräknad moms",
     "col_debit": "Debet",
     "col_credit": "Kredit",
     "vat_rate_presets_aria": "Välj momssats från lista",