🚸(frontend) make explicit why a page is not found

Enhance the error message based on @spaccoud's feedback,
explain to the user why a page is not found.

src/frontend/src/components/NotFoundScreen.tsx

@@ -1,12 +1,19 @@
 import { CenteredContent } from '@/layout/CenteredContent'
 import { Screen } from '@/layout/Screen'
+import { Text } from '@/primitives/Text'
 import { useTranslation } from 'react-i18next'
+import { Bold } from '@/primitives'
 
 export const NotFoundScreen = () => {
   const { t } = useTranslation()
   return (
     <Screen layout="centered">
-      <CenteredContent title={t('notFound.heading')} withBackButton />
+      <CenteredContent title={t('notFound.heading')} withBackButton>
+        <Text centered>
+          {t('notFound.body')}{' '}
+          <Bold>https://visio.numerique.gouv.fr/xxx-yyyy-zzz.</Bold>
+        </Text>
+      </CenteredContent>
     </Screen>
   )
 }

src/frontend/src/locales/de/global.json

@@ -22,7 +22,8 @@
   },
   "logout": "",
   "notFound": {
-    "heading": ""
+    "heading": "",
+    "body": ""
   },
   "submit": "OK",
   "footer": {

src/frontend/src/locales/en/global.json

@@ -22,7 +22,8 @@
   },
   "logout": "Logout",
   "notFound": {
-    "heading": "Page not found"
+    "heading": "Verify your meeting code",
+    "body": "Check that you have entered the correct meeting code in the URL. Example:"
   },
   "submit": "OK",
   "footer": {

src/frontend/src/locales/fr/global.json

@@ -22,7 +22,8 @@
   },
   "logout": "Se déconnecter",
   "notFound": {
-    "heading": "Page introuvable"
+    "heading": "Vérifier votre code de réunion",
+    "body": "Vérifiez que vous avez saisi le code de réunion correct dans l'URL. Exemple :"
   },
   "submit": "OK",
   "footer": {