v1.0.0

fix: restore capacity-aware overlap check in booking trigger

Ports SaaS migration 051. This repo was still on migration 019's version
of check_slot_availability(): exact-overlap check with capacity counting.
Combines the interval-overlap fix (handles bookings that overlap without
sharing the same starts_at, and NULL-safe ends_at for legacy rows) with the
capacity counting that group bookings (services.capacity > 1) rely on.
search_path = public kept inline since CREATE OR REPLACE FUNCTION resets
proconfig unless respecified (hardened here in migration 030).

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>