Timeline playback system

TimelineProvider (rAF playback, 1x/2x/4x/8x speed, 24h/3d/7d/all range, seekTo, loop), TimelineBar (draggable amber scrubber, day ticks, event density histogram, keyboard shortcuts), PlaybackControls (play/pause, speed/range pills, analytics), EventCard (type/confidence badges, casualties, sources). Timeline explorer page with server+client split.