Replace the lifetime "devices seen since start" counter in the mDNS, SSDP
and DHCP scanners with a rolling count of distinct devices (deduped by
MAC) seen within the last hour.
Each scanner's status now tracks a MAC -> last-seen-time map; the snapshot
prunes entries older than 60 minutes and reports the remaining count. The
API field name (devices_seen) is unchanged, so only its meaning and the
frontend labels ("N devices in the last hour") are updated.
Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
Add a DHCP scanner card to the Status screen and a DHCP row to the
consolidated Status card on the Home screen, mirroring the existing
mDNS/SSDP implementations. Also label DHCP-discovered device events as
"DHCP" instead of the raw "Dhcp".
Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
