Replace DayOfWeek with chrono::Weekday via extension traits, unify
RateLimitConfig into the config module, and remove the unused time
command, BannerState, and ClassDetails stub. Fix open_only query
parameter to respect false values and correct 12-hour time display.
Replace task abortion with broadcast-based graceful shutdown for scheduler and workers. Implement cancellation tokens for in-progress work with 5s timeout. Add tokio-util dependency for CancellationToken support. Update ServiceManager to use completion channels and abort handles for better service lifecycle control.
