Flame graph zoom + pan + minimap

[rohitg00]

web/src/components/traces/FlameGraph.tsx currently renders a static canvas — no zoom, no pan, no minimap.

Tasks:

• ctrl+wheel zoom around the cursor (zoomLevel 0.9/1.1 per tick)
• mousewheel pans panOffset along the time axis
• minimap canvas (32px tall) when zoomLevel > 1, with accent-outlined viewport indicator
• hover tooltip showing span name, service, duration, self-time, %trace, child count
• ResizeObserver already wired; extend to redraw on zoom/pan

Reference: workers/console/web/src/pages/Traces/components/FlameGraph.tsx (845 lines, has the full implementation).