refactor: separate unit in temperature sensors

Do not append the `°C` unit to temperature sensors.
Add the unit in a separate label key with `#unit` suffix.

This allows filtering out the unit label if the panel has a graphical
representation of the unit.

crates/aster-sysinfo/src/main.rs

@@ -401,8 +401,8 @@ impl SysinfoSource {
                     //          component.label(), component.type_id(), component.id());
                 }
 
-                // TODO add unit as a separate sensor?
-                add_sensor(sensors, label, format!("{temperature:.1} °C"));
+                add_sensor(sensors, format!("{label}#unit"), "°C");
+                add_sensor(sensors, label, format!("{temperature:.1}"));
             }
         }