feat: Match official app's advert import and discovery flow

- pushAdvert (0x80): import advert into firmware via cmdGetAdvertPath
  before fetching contact, so name/type/location are available
- pushNewAdvert (0x8A): fire-and-forget importReceivedAdvert to store
  contact in firmware (data already in push payload)
- controlData (0x8E) discovery: no firmware import (matches official app),
  just lookup existing contacts and show generic labels for unknown nodes
- Update meshcore_client git ref to bcbeff0 (burst sync + advert import)

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

pubspec.yaml

@@ -44,7 +44,7 @@ dependencies:
   meshcore_client:
     git:
       url: https://github.com/dz0ny/meshcore_client.git
-      ref: "f600789fac7f743b1c7db8aa24e441405413f669"
+      ref: "bcbeff09e6a56af3d54b884c4c503e30596195ab"
 
   # Codec2 ultra-low-bitrate speech codec (FFI plugin)
   codec2_flutter: