GetOrCreateProgressAsync now persists the new row itself and catches
DbUpdateException on unique-constraint violations — concurrent /info
calls no longer throw 500s. BattlePassService no longer calls
SaveChangesAsync after the get-or-create. FormatWireDate uses a named
JstOffset constant instead of an inline TimeSpan.FromHours(9).
Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>
Also fixes BattlePassRepository.GetActiveSeasonAsync to use client-side
DateTimeOffset filtering (SQLite provider cannot translate DateTimeOffset
comparisons in LINQ WHERE/ORDER BY clauses).
