v1.0.4 — bulk_fetch CSV cache closed_date + timestamp fidelity

Patch release. Fixes a data-fidelity regression in bulk_fetch's CSV cache surfaced by a cold-run rebuild of the resolution-equity case study: cached snapshots shipped an empty closed_date column and truncated timestamps to whole days, making resolution-time analyses impossible.

Fixed

• _write_record_row (bulk-cache writer) omitted closed_date entirely and wrote created_date at day grain. Cached and exported CSVs now round-trip full Socrata timestamps; date-only inputs unchanged.

Added

• ServiceRequestRecord.created_at / closed_at — optional full-precision datetime fields, populated whenever the source carries a time component. The day-grain created_date / closed_date fields stay authoritative and backward-compatible; use closed_at - created_at for hour-precision resolution latency.

Additive and backward-compatible. See changelog.