/portal overview: client's active sound locations as live tiles (current Lp +
Live/Stopped badge + "updated Xm ago", polled from the scoped cache every 15s)
plus a Leaflet map of locations with coordinates. /portal/location/{id}: 404-gated
read-only live panel — Lp/Leq/Lmax/L1/L10 cards + a 4-line Chart.js trace
(backfilled from /history) + measuring/freshness badge. Cache-only, 15s poll, no
device controls, no refresh-from-device. _client_locations() feeds the overview.
Verified: portal.py compiles; both inline scripts balance; all four portal
templates parse in Jinja2.
Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
