fix: phone provider (#44974)

fixes phone provider saves that showed success but did not persist the
enabled state
(smol regression from the refactor)


## ref:
- closes https://github.com/supabase/supabase/issues/44966

ig was introduced by 6b35cc8034


<!-- This is an auto-generated comment: release notes by coderabbit.ai
-->
## Summary by CodeRabbit

* **Bug Fixes**
* Automatically clears certain conditional fields when their visibility
condition becomes false to avoid stale values.
* Preserves input values and registration state for fields removed from
the UI (they no longer unregister on hide), improving form continuity
during toggles.
<!-- end of auto-generated comment: release notes by coderabbit.ai -->

apps/studio/components/interfaces/Auth/AuthProvidersForm/FormField.tsx

@@ -1,6 +1,7 @@
 import { format } from 'date-fns'
 import { CalendarIcon, ExternalLink } from 'lucide-react'
-import { type Control } from 'react-hook-form'
+import { useEffect } from 'react'
+import { useFormContext, type Control } from 'react-hook-form'
 import ReactMarkdown from 'react-markdown'
 import {
   Button,
@@ -53,6 +54,7 @@ const FormField = ({
   disabled: disabledProp,
   readOnly,
 }: FormFieldProps) => {
+  const { setValue } = useFormContext()
   const { description: originalDescription } = properties
   let description = originalDescription
 
@@ -79,6 +81,12 @@ const FormField = ({
     disabled: properties.show == null,
   })
 
+  useEffect(() => {
+    if (properties.show?.key != null && !showValue && fieldValue !== '') {
+      setValue(name, '', { shouldDirty: true })
+    }
+  }, [fieldValue, name, properties.show?.key, setValue, showValue])
+
   if (properties.show) {
     if (properties.show.matches) {
       if (!properties.show.matches.includes(showValue)) {
@@ -341,7 +349,7 @@ const FormField = ({
                 >
                   <FormControl_Shadcn_ className="col-span-6">
                     <Select_Shadcn_
-                      defaultValue={properties.enum[0]}
+                      defaultValue={properties.enum[0]?.value}
                       value={field.value}
                       onValueChange={field.onChange}
                     >

apps/studio/components/interfaces/Auth/AuthProvidersForm/ProviderForm.tsx

@@ -165,7 +165,7 @@ export const ProviderForm = ({ config, provider, isActive }: ProviderFormProps)
   const form = useForm({
     defaultValues: INITIAL_VALUES,
     resolver: zodResolver(provider.validationSchema),
-    shouldUnregister: true,
+    shouldUnregister: false,
   })
 
   useEffect(() => {