fix(fridge): stop switch turn-off silently sending 'On'

Six fridge SwitchDesc write_fns built their payload with
`'On' if p else 'Off'`. The switch platform passes the literal
string 'Off' on turn-off, which is truthy, so the guard always
produced 'On' -- turning these switches off silently re-sent On
and they could never be turned off:

  - ICEMAKER_NIGHTTIME (ice.night.status)
  - STATUS_LOCK helper (devicecontrol + device.sound)
  - DEFROST_DELAY (delayDefrost)
  - WELCOME_LIGHTING (status)
  - CABINET_LIGHT dim (light.dimming.status)
  - ICEMAKER_STATUS_FALLBACK (iceMaker)

Compare `p == 'On'` instead, matching the pattern the other
capability files already use. Adds a regression test asserting
every affected write_fn sends 'Off' on 'Off' and 'On' on 'On'.

custom_components/localthings/registry/capabilities/fridge.py

@@ -92,7 +92,7 @@ ICEMAKER_NIGHTTIME = Capability(
                    value_fn=lambda v: v == 'On',
                    write_fn=lambda p, rep, href=None: (
                        ['icemaker', 'nighttime', 'vs', '0'],
-                       {'ice.night.status': 'On' if p else 'Off'})),
+                       {'ice.night.status': 'On' if p == 'On' else 'Off'})),
     ),
 )
 
@@ -168,7 +168,7 @@ DOOR_ALERT = Capability(
 def _status_lock_write(field):
     return lambda p, rep, href=None: (
         ['status', 'lock', 'vs', '0'],
-        {field: 'On' if p else 'Off'}
+        {field: 'On' if p == 'On' else 'Off'}
     )
 
 
@@ -212,7 +212,7 @@ DEFROST_DELAY = Capability(
                    value_fn=lambda v: v == 'On',
                    write_fn=lambda p, rep, href=None: (
                        ['defrost', 'delay', 'vs', '0'],
-                       {'x.com.samsung.da.delayDefrost': 'On' if p else 'Off'})),
+                       {'x.com.samsung.da.delayDefrost': 'On' if p == 'On' else 'Off'})),
     ),
 )
 
@@ -300,7 +300,7 @@ WELCOME_LIGHTING = Capability(
                    value_fn=lambda v: v == 'On',
                    write_fn=lambda p, rep, href=None: (
                        ['proximity', 'vs', '0'],
-                       {'status': 'On' if p else 'Off'})),
+                       {'status': 'On' if p == 'On' else 'Off'})),
     ),
 )
 
@@ -440,7 +440,7 @@ CABINET_LIGHT = Capability(
                    value_fn=lambda v: v == 'On',
                    write_fn=lambda p, rep, href=None: (
                        ['cabinet', 'light', 'total', 'vs', '0'],
-                       {'light.dimming.status': 'On' if p else 'Off'})),
+                       {'light.dimming.status': 'On' if p == 'On' else 'Off'})),
     ),
 )
 
@@ -669,7 +669,7 @@ ICEMAKER_STATUS_FALLBACK = Capability(
                    value_fn=lambda v: v == 'On',
                    write_fn=lambda p, rep, href=None: (
                        ['icemaker', 'status', 'vs', '0'],
-                       {'x.com.samsung.da.iceMaker': 'On' if p else 'Off'})),
+                       {'x.com.samsung.da.iceMaker': 'On' if p == 'On' else 'Off'})),
     ),
 )