feat: remove appwrite and add nextjs backend

.env.example

@@ -1,9 +1,15 @@
-# Appwrite
-APPWRITE_FUNCTION_API_KEY=your-api-key
-PUBLIC_APPWRITE_HOST=http://localhost/v1
+# DATABASE
+DB_URL="postgresql://${DB_USER}:${DB_PASSWORD}@${DB_HOST}/pingvin-share?schema=public"
+DB_USER=postgres
+DB_PASSWORD=postgres
+DB_HOST=db:5432
 
-# Frontend
-PUBLIC_MAX_FILE_SIZE=300000000 # Note: Should be the same as in the _APP_STORAGE_LIMIT in the Appwrite .env file
-PUBLIC_DISABLE_REGISTRATION=true # Note: In the Appwrite console you have to change your user limit to 0 if false and else to 1
-PUBLIC_DISABLE_HOME_PAGE=false
-PUBLIC_MAIL_SHARE_ENABLED=false # Note: If set to true you have to add your SMTP server. See "Additional configurations" in the README file
+# GENERAL
+APP_URL=http://localhost:3000
+BACKEND_URL=http://backend:8080
+SHOW_HOME_PAGE=true
+ALLOW_REGISTRATION=true
+MAX_FILE_SIZE=1000000000
+
+# SECURITY
+JWT_SECRET=long-random-string