v0.4.2 - Timezone-Safe Fortnights

Summary

• Fix transaction visibility on the first local day of a fortnight by using timezone-aware UTC bounds.
• Fortnight creation now stores local dates + timezone and derives UTC bounds consistently.
• Added backfill tooling for existing databases.

Migration (required if you already have data)

1. Run: psql < backend/migrations/003-backfill-fortnight-timezone-bounds.sql
2. Or: pnpm --filter backend db:backfill-fortnight-bounds
3. Restart backend.

Why this matters

Transactions recorded on the first local morning (UTC+ timezones) were previously outside the UTC-based fortnight window. This release fixes that for all locales.