* fix: use range overlap for duplicate period check (BFL 4:1 compliance)
The period duplicate check used exact-match on fiscal_year_start/end, missing
overlapping periods (e.g., partial-year file vs full-year import). Now uses
standard interval overlap test (start <= other_end AND end >= other_start).
Updated Swedish error messages to reflect overlap semantics.
Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
* fix: align JSDoc citation to BFL 4:1 for period overlap check
Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
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Co-authored-by: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
Jakob Wennberg
8855ef1485