fix: persist failureSensorType to JSON config by marking it required in schema (#245)

* Initial plan

* fix: add failureSensorType to schema required fields to prevent UI reversion

Agent-Logs-Url: https://github.com/homebridge-plugins/homebridge-updater/sessions/fb682c05-a5ad-42aa-8797-ed2322f46498

Co-authored-by: donavanbecker <9875439+donavanbecker@users.noreply.github.com>

---------

Co-authored-by: copilot-swe-agent[bot] <198982749+Copilot@users.noreply.github.com>
Co-authored-by: donavanbecker <9875439+donavanbecker@users.noreply.github.com>

Author: Copilot

config.schema.json

@@ -222,7 +222,7 @@
         "properties": {}
       }
     },
-    "required": ["name", "sensorType"]
+    "required": ["name", "sensorType", "failureSensorType"]
   },
   "layout": [
     "name",

src/schema.test.ts

@@ -41,6 +41,7 @@ describe('config schema validation', () => {
         const config = {
           name,
           sensorType: 'motion',
+          failureSensorType: 'motion',
           platform: 'HomebridgeUpdater',
         }
 
@@ -118,6 +119,7 @@ describe('config schema validation', () => {
       const config = {
         name: maxLengthName,
         sensorType: 'motion',
+        failureSensorType: 'motion',
         platform: 'HomebridgeUpdater',
       }