feat: add solar return energy to home assistant

hosts/sausebiene/hass-modbus/mennekes-amtron-xtra.nix

@@ -47,6 +47,7 @@
         ];
       }
     ];
+
     template = [
       {
         sensor = [

hosts/sausebiene/home-assistant.nix

@@ -43,6 +43,7 @@ in
     enable = true;
     extraComponents = [
       "esphome"
+      "forecast_solar"
       "fritzbox"
       "matter"
       "met"
@@ -160,6 +161,26 @@ in
           types = [ "Papiermüll" ];
         }
       ];
+
+      template = [
+        {
+          sensor = [
+            {
+              name = "Total Grid Return Energy";
+              unique_id = "calculated_total_grid_return_energy";
+              device_class = "energy";
+              unit_of_measurement = "kWh";
+              state_class = "total_increasing";
+              state = ''
+                {% set solar = states('sensor.pro3em_solar_total_active_energy') | float(0) %}
+                {% set mains = states('sensor.pro3em_mains_total_active_energy') | float(0) %}
+                {% set export = solar - mains %}
+                {{ [export, 0] | max }}
+              '';
+            }
+          ];
+        }
+      ];
     };
 
     extraPackages =