Show banner on dates <= cutoff instead of only == cutoff

Users won't be given access until near the date, and if they log on a
bit early, then it'll still be useful information for them.

Jira-Issue: MAV-5301

Author: alistair-white-horne-tng

app/views/immunisation_imports/new.html.erb

@@ -6,7 +6,7 @@
 
 <% content_for :page_title, title %>
 
-<% if (cutoff_date = current_team.national_reporting_cut_off_date) && cutoff_date.today? %>
+<% if (cutoff_date = current_team.national_reporting_cut_off_date) && Date.today <= cutoff_date %>
   <%= govuk_notification_banner(title_text: "Important") do %>
     <h3 class="nhsuk-notification-banner__heading">
       Mavis national reporting replaces NIVS on <%= cutoff_date.to_fs(:long) %>

spec/features/import_vaccination_records_national_reporting_spec.rb

@@ -56,8 +56,8 @@
   context "cutoff date banner" do
     let(:cutoff_date) { Date.new(2026, 4, 20) }
 
-    context "when today is not the cutoff date" do
-      around { |example| travel_to(cutoff_date - 1.day) { example.run } }
+    context "when today is after the cutoff date" do
+      around { |example| travel_to(cutoff_date + 1.day) { example.run } }
 
       scenario "banner is not shown" do
         given_mavis_logins_are_configured(
@@ -69,6 +69,22 @@
       end
     end
 
+    context "when today is before the cutoff date" do
+      around { |example| travel_to(cutoff_date - 1.day) { example.run } }
+
+      scenario "banner is shown" do
+        given_mavis_logins_are_configured(
+          national_reporting_cut_off_date: cutoff_date
+        )
+        given_i_am_signed_in_as_a_national_reporting_user
+        when_i_navigate_to_the_upload_page
+        expect(page).to have_css(".nhsuk-notification-banner")
+        expect(page).to have_content(
+          "Mavis national reporting replaces NIVS on 20 April 2026"
+        )
+      end
+    end
+
     context "when today is the cutoff date" do
       around { |example| travel_to(cutoff_date) { example.run } }