fix: allow popup overflow for floor dropdown visibility

Set overflow: visible on MapLibre popup to prevent clipping
of floor select dropdown when it expands.

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

TODO.md

@@ -34,7 +34,7 @@
 - [x] Source scanner tracking for synced devices
 - [x] Peer scanner markers on map
 - [x] Background sync thread
-- [ ] WebSocket real-time sync (instead of polling)
+- [x] WebSocket real-time sync (instead of polling)
 - [ ] Automatic peer discovery via mDNS/Bonjour
 - [ ] Sync RSSI history for trilateration
 - [ ] Web UI for peer management
@@ -120,7 +120,7 @@
 ## API & Integration
 
 - [ ] OpenAPI/Swagger documentation
-- [ ] WebSocket for real-time updates
+- [x] WebSocket for real-time updates
 - [ ] GraphQL endpoint (optional)
 - [ ] MQTT publishing
 - [x] Home Assistant webhook integration (scan results, new device, departure)