Change date helper functions to use toLocaleDateString with the
configured SCRAPER_TIMEZONE (America/Denver) so that scrape date
records (date_checked, daily summaries) reflect local time. A
late-night manual scrape and early-morning automated scrape will
no longer both report as the same UTC day.
ISO timestamps for last_scraped, first_seen, startedAt etc. remain
in UTC as they represent precise moments.
