feat: infer uprn_known as No if the user answers address (through "Enter address instead" route/check answers page)

app/models/derived_variables/lettings_log_variables.rb

@@ -95,6 +95,8 @@ module DerivedVariables::LettingsLogVariables
 
     set_housingneeds_fields if housingneeds?
 
+    self.uprn_known = 0 if address_answered?
+
     if uprn_known&.zero?
       self.uprn = nil
     end
@@ -310,6 +312,10 @@ private
     self.county = nil
   end
 
+  def address_answered?
+    [address_line1, town_or_city].all?(&:present?)
+  end
+
   def get_lar
     return 1 if rent_type == 2
     return 2 if rent_type == 1