🚧 Migrate env variables to use internal SvelteKit system

Some API fetching function rewriting needed as privates cannot be included into public code

src/routes/api/newsletter/+server.ts

@@ -1,5 +1,6 @@
 import { error } from '@sveltejs/kit'
 import type { RequestHandler } from './$types'
+import { NEWSLETTER_API_TOKEN, NEWSLETTER_LIST_ID } from '$env/static/private'
 
 
 export const POST: RequestHandler = async ({ request }) => {
@@ -7,11 +8,11 @@ export const POST: RequestHandler = async ({ request }) => {
         const body = await request.text()
 
         if (body) {
-            const req = await fetch(`https://emailoctopus.com/api/1.6/lists/${import.meta.env.VITE_NEWSLETTER_LIST_ID}/contacts`, {
+            const req = await fetch(`https://emailoctopus.com/api/1.6/lists/${NEWSLETTER_LIST_ID}/contacts`, {
                 method: 'POST',
                 headers: { 'Content-Type': 'application/json' },
                 body: JSON.stringify({
-                    api_key: import.meta.env.VITE_NEWSLETTER_API_TOKEN,
+                    api_key: NEWSLETTER_API_TOKEN,
                     email_address: body,
                 })
             })