Breville easyair/Catit fountain: fix day units, use duration class

day/days should be "d", per HA UnitOfTime mapping.
Once the units are correct, we can use a class of duration for these sensors.

custom_components/tuya_local/devices/breville_easyair_purifier.yaml

@@ -44,12 +44,13 @@ secondary_entities:
   - entity: sensor
     name: Filter days left
     category: diagnostic
+    class: duration
     icon: "mdi:air-filter"
     dps:
       - id: 16
         name: sensor
         type: integer
-        unit: day
+        unit: d
   - entity: select
     name: Timer
     icon: "mdi:fan-clock"

custom_components/tuya_local/devices/catit_pixi_smart_fountain.yaml

@@ -32,6 +32,7 @@ secondary_entities:
     name: Filter life
     icon: "mdi:air-filter"
     category: diagnostic
+    class: duration
     dps:
       - id: 4
         type: integer
@@ -43,7 +44,7 @@ secondary_entities:
           - scale: 1440 # minutes => days
             step: 1
             invert: true
-        unit: days
+        unit: d
 
   - entity: switch
     name: Run UV cycle