Feedback command added; search gets time-window filters

4a72ff1: Add releases feedback to send feedback about the CLI (arg, stdin, or interactive; --contact, --type, --json, --dry-run), and releases admin feedback list to review submissions.
62f7f78: Add --since / --until time-window filters to releases search and releases tail|latest. Each accepts an ISO date (2026-01-01) or relative shorthand (90d, 4w, 6m, 2y) and filters releases by publish date, composing with the existing filters. Enables capability-discovery queries like releases search "slack integration" --since 90d.