Show error on invalid API key

app/models/family.rb

@@ -162,6 +162,10 @@ def synth_overage?
     self.class.synth_provider&.usage&.utilization.to_i >= 100
   end
 
+  def synth_valid?
+    self.class.synth_provider&.healthy?
+  end
+
   def subscribed?
     stripe_subscription_status == "active"
   end

app/views/pages/dashboard.html.erb

@@ -4,6 +4,11 @@
       Your Synth API credit limit has been exceeded. Please visit your <a href="https://dashboard.synthfinance.com/settings" class="font-medium underline hover:text-yellow-900">Synth billing settings</a> to upgrade your plan or wait for your credits to reset.
     </div>
   <% end %>
+  <% if self_hosted? && !Current.family&.synth_valid? %>
+    <div class="bg-yellow-100 border border-yellow-400 text-yellow-700 px-4 py-3 rounded relative" role="alert">
+      Your Synth API Key is invalid. Please visit your <a href="https://dashboard.synthfinance.com/dashboard" class="font-medium underline hover:text-yellow-900">Synth dashboard</a> and verify that your API key is correct.
+    </div>
+  <% end %>
   <header class="flex items-center justify-between">
     <div>
       <h1 class="sr-only"><%= t(".title") %></h1>