fix(ui): Kobalte Select sentinel + drop superseded reset block
Kobalte Select treats empty string as no value and throws when an
option carries value: "". Replace with explicit STATUS_ALL/SINCE_ALL
sentinels in the Dashboard history filters and update the dependent
status/since query-param logic.
Also drop the * { box-sizing/margin/padding } reset block from
styles.css — Tailwind v4 preflight already handles it, and the
duplicate rule was contributing 8 lines of dead CSS to every build.