Apple Fitness workout fixer + Strava uploader

Replace edit view with activity graph + range slider for workout trimming master

- Add ActivityGraphView (Swift Charts line/area graph with dimming overlays) - Add RangeSliderView (two-thumb slider for selecting trim range) - Rewrite WorkoutEditView: graph, slider, time labels, activity picker - Expand HealthKitManager with HR/energy/distance queries and realistic sample data - Add destructive action warning to save confirmation - Remove WorkoutAddView (not a use-case)