feat: remove appwrite and add nextjs backend

backend/.env.example

@@ -0,0 +1,12 @@
+# Environment variables declared in this file are automatically made available to Prisma.
+
+DB_URL="postgresql://${DB_USER}:${DB_PASSWORD}@${DB_HOST}/pingvin-share?schema=public"
+DB_USER=postgres
+DB_PASSWORD=postgres
+DB_HOST=localhost:5432
+
+APP_URL=http://localhost:3000
+ALLOW_REGISTRATION=true
+MAX_FILE_SIZE=5000000000
+
+JWT_SECRET=csdkdfmfdfdkslfjskl3987rfkhjgdfnkjdf