* fix(bookkeeping): let a backfilled first räkenskapsår start mid-month (#2237)
POST /api/bookkeeping/fiscal-periods decided "first period" as "no period
exists at all", so a company that imported 2024+ from Fortnox and then
created its actual first year by hand (2022-07-22, the registration date)
was refused with the 1st-of-month error, while the DB trigger
enforce_first_of_month_for_subsequent_periods would have accepted the row.
The route now mirrors the trigger: first = no existing period starts
earlier. The 1st-of-month rule (BFL 3 kap. 1 §) keeps binding subsequent
years, and its message now says which years it binds and why instead of
only refusing.
Tests: prepend with a mid-month start passes; a mid-month start for a
non-earliest period is still a 400 that names the rule.
Closes#2237
Co-Authored-By: Claude Fable 5.1 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01VnConrmMCxJRQ5kfiPPWyy
* chore: carry the DECISIONS.md line for this PR in #2247 instead (append-only log conflicts on every merge)
---------
Co-authored-by: Jakob Wennberg <311770904+jakobwennberg-oss@users.noreply.github.com>
Co-authored-by: Claude Fable 5.1 <noreply@anthropic.com>