increase CR for off grid

default should be higher assuming trees etc

lib/models/radio_settings.dart

@@ -228,7 +228,7 @@ class RadioSettings {
         frequencyMHz: 433.0,
         bandwidth: LoRaBandwidth.bw250,
         spreadingFactor: LoRaSpreadingFactor.sf11,
-        codingRate: LoRaCodingRate.cr4_5,
+        codingRate: LoRaCodingRate.cr4_8,
         txPowerDbm: 20,
       ),
     ),
@@ -238,7 +238,7 @@ class RadioSettings {
         frequencyMHz: 869.0,
         bandwidth: LoRaBandwidth.bw250,
         spreadingFactor: LoRaSpreadingFactor.sf11,
-        codingRate: LoRaCodingRate.cr4_5,
+        codingRate: LoRaCodingRate.cr4_8,
         txPowerDbm: 14,
       ),
     ),
@@ -248,7 +248,7 @@ class RadioSettings {
         frequencyMHz: 918.0,
         bandwidth: LoRaBandwidth.bw250,
         spreadingFactor: LoRaSpreadingFactor.sf11,
-        codingRate: LoRaCodingRate.cr4_5,
+        codingRate: LoRaCodingRate.cr4_8,
         txPowerDbm: 20,
       ),
     ),