[CPT Mailer] Switch to PNGs for receipt status image

app/controllers/hcb_codes_controller.rb

@@ -206,7 +206,13 @@ def receipt_status
     @secret = params[:s]
     @hcb_code = HcbCode.find_signed(@secret, purpose: :receipt_status)
 
-    raise Pundit::NotAuthorizedError if @hcb_code.nil?
+    if @hcb_code.nil?
+      raise Pundit::NotAuthorizedError
+    end
+
+    file_name = @hcb_code.missing_receipt? ? "receipt_status_upload.png" : "receipt_status_uploaded.png"
+
+    send_file Rails.root.join("app", "assets", "images", file_name), type: "image/png", disposition: "inline"
   end
 
   def toggle_tag

app/views/canonical_pending_transaction_mailer/_attach_receipt.html.erb

@@ -1,7 +1,7 @@
 <% if hcb_code.receipt_required? %>
 
   <%= link_to upload_url do %>
-    <img style="display: block; margin-top: 10px;" src="<%= receipt_status_hcb_codes_url(format: :svg, s: @cpt.local_hcb_code.signed_id(purpose: :receipt_status)) %>" alt="Click to upload your receipt">
+    <img style="display: block; margin-top: 10px;" src="<%= receipt_status_hcb_codes_url(format: :png, s: @cpt.local_hcb_code.signed_id(purpose: :receipt_status)) %>" alt="Click to upload your receipt">
   <% end %>
   <p><em>This link can be used by anyone for two weeks to upload a receipt for this charge.</em></p>