Remove unused base year from Context and use only .env config

src/routes/__layout.svelte

@@ -45,9 +45,6 @@
     writable({})
   setContext("variableValuesByName", variableValuesByName)
 
-  const year = writable(2021)
-  setContext("year", year)
-
   if (browser && matomoConfig !== undefined) {
     matomo(matomoConfig.siteId, matomoConfig.url)
   }