feat: add Show Page Emails tab (#2962)

* feat: add Show Page Emails tab

Closes #2926, Closes #2927

* feat: review - disable Emails tab if messaging not enabled

* refactor: review - add FeatureFlagKey type

---------

Co-authored-by: Thais GUIGON <thaisguigon@macbook-pro.home>

packages/twenty-front/src/modules/activities/emails/components/Emails.tsx

@@ -0,0 +1,38 @@
+import styled from '@emotion/styled';
+
+import {
+  H1Title,
+  H1TitleFontColor,
+} from '@/ui/display/typography/components/H1Title';
+import { Section } from '@/ui/layout/section/components/Section';
+
+const StyledContainer = styled.div`
+  display: flex;
+  flex-direction: column;
+  gap: ${({ theme }) => theme.spacing(6)};
+  padding: ${({ theme }) => theme.spacing(6, 6, 2)};
+`;
+
+const StyledH1Title = styled(H1Title)`
+  display: flex;
+  gap: ${({ theme }) => theme.spacing(2)};
+`;
+
+const StyledEmailCount = styled.span`
+  color: ${({ theme }) => theme.font.color.light};
+`;
+
+export const Emails = () => (
+  <StyledContainer>
+    <Section>
+      <StyledH1Title
+        title={
+          <>
+            Inbox <StyledEmailCount>2</StyledEmailCount>
+          </>
+        }
+        fontColor={H1TitleFontColor.Primary}
+      />
+    </Section>
+  </StyledContainer>
+);