add actors-indexed trend chart, hourly snapshots, fix rate limit UX
replace the 4-metric grid on /stats with a canvas line chart showing
total actors, with handles, and with avatars over time. chart uses
multi-layered glow rendering inspired by relay-eval, with hover
crosshair + tooltip and touch support for mobile.
new snapshots table records actor counts hourly (first uncached search
per hour triggers a snapshot via KV flag). live counts appended as the
latest point so the chart always extends to now.
also fixes /request-indexing rate limiting: returns HTML with a friendly
message instead of raw JSON, and uses the standard rate limiter (60/min)
with a namespaced key instead of the strict limiter.
Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>