v0.6.3: Add search + capped rendering to consumer view

Add an in-card search box for consumer messages (searches payload, routing key, exchange and correlation id) and limit actual rendered rows with a RENDER_CAP (200) to improve performance. Show total received counts (with tooltip) and buffered/capped state; clear/stop buttons now consider received totals. Update LeftPanel to display the received count with a tooltip. Underlying consumerStore was adjusted to support received counters/capping.