fix(bookkeeping): a following year's own IB no longer blocks nollställ, and a re-dated räkenskapsår gets the right name (#2286)

Customer report (Aisen & Adison AB, 2026-09-03): Fortnox years 2024-2026
imported first, then the first year 2022/2023 backfilled. Two bugs surfaced.

1. The backfilled year was saved as "Räkenskapsår 2027": CreatePeriodDialog
   seeds the next forward year and kept that name when the user re-dated the
   form. The name now follows the typed dates until the user edits the name
   (fiscalYearName exported from suggest-fiscal-period).

2. Nollställ of the backfilled year was refused with next_year_dependency
   because 2024 carried an opening-balance verifikat. Any IB in the next year
   counted as reliance, so a backfilled year could never be reset, while a
   next year WITHOUT an IB (whose balansrapport really rolls from this year)
   was allowed. Migration 20260904163000 redefines fiscal_year_reset_snapshot:
   the block fires only when the next year is locked, closed or has its own
   closing entry; a bokslut-generated IB is still refused via this year's
   closing_entry_id (year_end_state). The snapshot returns next_period
   {id, name, has_opening_balances} and the dialog states that the following
   year's IB stays as it is.

pg-real: reset-fiscal-year.pg.test.ts pins the narrowed guard (closed next
year, next year with closing entry, next year with its own IB survives the
reset untouched).

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

types/index.ts

@@ -145,6 +145,14 @@ export interface FiscalYearResetEligibility {
     vouchers: number
     documents_to_detach: number
   }
+  // The following räkenskapsår, when one exists. Its own opening balances
+  // are never touched by the reset and are disclosed, not treated as a
+  // dependency (migration 20260904163000).
+  next_period: {
+    id: string
+    name: string
+    has_opening_balances: boolean
+  } | null
 }
 
 export interface FiscalYearResetRpcResult {
@@ -154,6 +162,7 @@ export interface FiscalYearResetRpcResult {
   blockers?: FiscalYearResetBlocker[]
   period?: FiscalYearResetEligibility['period']
   counts?: FiscalYearResetEligibility['counts']
+  next_period?: FiscalYearResetEligibility['next_period']
   deleted?: number
   detached_documents?: number
   period_name?: string