feat: data source toggles + HTTP status codes (upstream #242)

Port upstream PR #242 data layer: per-source enabled toggles and HTTP
status codes for custom data sources.

- IRemoteSource: NetworkResult(code, stream) + getNetworkStream
- RemoteSource: return HTTP status code (200 ok / error code / ERR)
- ISettingsRepo: dataSourcesStatus StateFlow<Map<String,Int>>
- SettingsRepo: persist enabled flags (single JSON per key) + status
- DatabaseRepo: filter by enabled toggles, write back status codes
- Settings.kt: DataSourcesSettings + satelliteEnabled/transceiversEnabled
- Sync test fakes (AmSatRepositoryTest, DatabaseRepoTest, Fakes.kt)

Fork-specific features preserved: builtinTypesByUrl reverse lookup,
satnogs migration, map-type data source structure.

feature/mutual/src/test/java/com/rtbishop/look4sat/feature/mutual/Fakes.kt

@@ -83,6 +83,11 @@ class FakeSettingsRepo(initialPosition: GeoPos = GeoPos(23.13, 113.26)) : ISetti
     override fun updateRCSettings(settings: RCSettings) = TODO()
     override fun updateOtherSettings(transform: (OtherSettings) -> OtherSettings) = TODO()
     override fun updateDataSourcesSettings(settings: DataSourcesSettings) = TODO()
+
+    override val dataSourcesStatus: StateFlow<Map<String, Int>> = MutableStateFlow(emptyMap())
+
+    override fun updateDataSourcesStatus(status: Map<String, Int>) = TODO()
+
     override fun updateRadioControlSettings(settings: RadioControlSettings) = TODO()
     override fun getSatelliteOffset(catnum: Int): String = ""
     override fun setSatelliteOffset(catnum: Int, offset: String) = TODO()