Internal quick build (debug)

Internal debug build of the System Fitbit Connector Android app (because debug build is fast and easiet for internal use). It runs a lightweight listener on the phone (port 3000) to receive sensor packets and forwards them to the PC Node server at http://:3168/data, resolving the destination IP via the new rendezvous API (no more MongoDB Realm/FCM). This build includes an editable device role (colour), a Refresh IP button with status messaging, improved reliability (byte-accurate reads, timeouts), and optional local JSONL backups for resilience on flaky networks. Intended for internal testing on the same Wi-Fi; sideload the APK.