fix: make useBooking submit() validate synchronously instead of racing setState's updater

src/hooks/useBooking.ts

@@ -55,22 +55,17 @@ export default function useBooking(initialServiceId?: string) {
   }, [])
 
   const submit = useCallback((): boolean => {
-    let result = false
-    setState((s) => {
     const nextErrors: BookingErrors = {}
-      if (!s.contact.name.trim()) nextErrors.name = 'Name is required.'
-      if (!isValidEmail(s.contact.email)) nextErrors.email = 'A valid email is required.'
-      if (!s.contact.phone.trim()) nextErrors.phone = 'Phone is required.'
+    if (!state.contact.name.trim()) nextErrors.name = 'Name is required.'
+    if (!isValidEmail(state.contact.email)) nextErrors.email = 'A valid email is required.'
+    if (!state.contact.phone.trim()) nextErrors.phone = 'Phone is required.'
     setErrors(nextErrors)
     if (Object.keys(nextErrors).length > 0) {
-        result = false
-        return s
+      return false
     }
-      result = true
-      return { ...s, step: 'confirmed' }
-    })
-    return result
-  }, [])
+    setState((s) => ({ ...s, step: 'confirmed' }))
+    return true
+  }, [state.contact])
 
   const reset = useCallback(() => {
     setState(initialState(initialServiceId))