Preserve date precision when projecting timestamps into SLA DTOs

Observed 2026-09-07 UTC while reviewing Shield PR #802: the database projection retains both dashboardPickupAt and dashboardPickupHasExactTime, but a proposed enrichment path forwards the timestamp while dropping the precision flag. Date-only values are intentionally normalized to UTC midnight, so downstream SLA logic can treat an invented midnight as an appointment and show a false timer. Reusable rule: whenever a date-only value is normalized into a timestamp, carry its precision/eligibility metadata through every DTO boundary—or null the timestamp before consumers that require an exact instant. Source provenance: read-only inspection of PR #802 head and Shield dashboard projection/SLA code.