Website UI design (#4829)

**Fixed different issues** :
 
- Multiple CSS fixes: font-size, colors, margins, z-index ...
- Fixed hover on contributor avatars
- Added link to contributors in footer
- Made the year in the footer dynamic (2023 --> 2024)
- Added name of contributor in "Thank you" section of Contributor page
- Added footer in small screens
- Made Activity Log Responsive 
- Fixed bug in "saving issues to DB", title was null everywhere. I
needed to implement an "upsert" behaviour to update the existing
database on init

**To be noted :** 

There is the following bug on production happening on mobile when you
refresh a second time :

<img width="1440" alt="Screenshot 2024-04-05 at 01 30 58"
src="https://github.com/twentyhq/twenty/assets/102751374/b935b07a-63dc-463d-8dcb-070ad4ef6db0">


It seems to be related to the following issue on mdx :
[https://github.com/hashicorp/next-mdx-remote/issues/350](https://github.com/hashicorp/next-mdx-remote/issues/350)

I added the following code that fixed this bug for me in development
(this needs to be tested in production) :

```
const serialized = await serialize(content, {
    mdxOptions: {
      development: process.env.NODE_ENV === 'development',
    }
  })
```

---------

Co-authored-by: Ady Beraud <a.beraud96@gmail.com>

packages/twenty-website/src/app/_components/contributors/ThankYou.tsx

@@ -6,7 +6,6 @@ import { CardContainer } from '@/app/_components/contributors/CardContainer';
 import { HeartIcon } from '@/app/_components/ui/icons/SvgIcons';
 
 const StyledTitle = styled.div`
-  display: flex;
   font-size: 24px;
   font-weight: 500;
   gap: 8px;
@@ -18,20 +17,21 @@ const StyledTitle = styled.div`
 
 const StyledHeartIcon = styled(HeartIcon)`
   @media (max-width: 810px) {
+    display: inline-block !important;
     width: 16px !important;
     height: 16px !important;
   }
 `;
 
 interface ThankYouProps {
-  authorId: string;
+  username: string;
 }
 
-export const ThankYou = ({ authorId }: ThankYouProps) => {
+export const ThankYou = ({ username }: ThankYouProps) => {
   return (
     <CardContainer>
       <StyledTitle>
-        Thank you @{authorId} <StyledHeartIcon color="#333333" size="18px" />
+        Thank you @{username} <StyledHeartIcon color="#333333" size="18px" />
       </StyledTitle>
     </CardContainer>
   );