Add "I deploy on Fridays" merch callout to UI and README (#1024)

* Add "I deploy on Fridays" merch callout to UI and README

Adds a small, muted tee callout in the Flipper UI footer (gated behind
the existing `fun` config) and a short Merch section in the README, with
specs covering the fun-mode toggle.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

* Move merch link to nav, keep Cloud as sole footer CTA

Per feedback, two footer CTAs side-by-side diluted the Flipper Cloud
callout. Move the tee to a small "Shirt" nav link (Docs • Shirt •
Version), leaving Cloud uncontested in the footer.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

---------

Co-authored-by: Claude Opus 4.8 <noreply@anthropic.com>

Author: jnunemaker

README.md

@@ -37,6 +37,10 @@ Or install it yourself with:
 
 [💌  Subscribe](https://blog.flippercloud.io/#/portal/signup) - we'll send you short and sweet emails when we release new versions ([examples](https://blog.flippercloud.io/tag/releases/)).
 
+## Merch
+
+Do you deploy on Fridays? [👕 Get the tee](https://shop.verygoodsoftware.company/product/i-deploy-on-fridays-tee?utm_source=oss&utm_medium=readme&utm_campaign=merch).
+
 ## Getting Started
 
 Use `Flipper#enabled?` in your app to check if a feature is enabled.

lib/flipper/ui/views/layout.erb

@@ -57,6 +57,10 @@
           <li class="nav-item ms-auto text-muted small">
             <a href="https://www.flippercloud.io/docs/ui?utm_source=oss&utm_medium=ui&utm_campaign=docs">Docs</a>
             &bull;
+            <% if Flipper::UI.configuration.fun %>
+              <a href="https://shop.verygoodsoftware.company/product/i-deploy-on-fridays-tee?utm_source=oss&utm_medium=ui&utm_campaign=merch" title="Do you deploy on Fridays?">Shirt</a>
+              &bull;
+            <% end %>
             Version: <%= Flipper::VERSION %>
           </li>
         </ul>

spec/flipper/ui/actions/features_spec.rb

@@ -86,6 +86,36 @@
       end
     end
 
+    context "merch callout" do
+      before do
+        @original_fun_enabled = Flipper::UI.configuration.fun
+        Flipper::UI.configuration.fun = fun_mode
+        get '/features'
+      end
+
+      after do
+        Flipper::UI.configuration.fun = @original_fun_enabled
+      end
+
+      context "when fun mode is enabled" do
+        let(:fun_mode) { true }
+
+        it 'renders the shirt link' do
+          expect(last_response.body).to include('>Shirt</a>')
+          expect(last_response.body).to include('i-deploy-on-fridays-tee')
+        end
+      end
+
+      context "when fun mode is disabled" do
+        let(:fun_mode) { false }
+
+        it 'does not render the shirt link' do
+          expect(last_response.body).not_to include('>Shirt</a>')
+          expect(last_response.body).not_to include('i-deploy-on-fridays-tee')
+        end
+      end
+    end
+
     context "when in read-only mode" do
       before { allow(flipper).to receive(:read_only?) { true } }