fix: improve self-host convenience (#5582)

packages/backend/server/.env.example

@@ -1,8 +1,4 @@
-DATABASE_URL="postgresql://affine@localhost:5432/affine"
-NEXTAUTH_URL="http://localhost:8080"
-OAUTH_EMAIL_SENDER="noreply@toeverything.info"
-OAUTH_EMAIL_LOGIN=""
-OAUTH_EMAIL_PASSWORD=""
-ENABLE_LOCAL_EMAIL="true"
-STRIPE_API_KEY=
-STRIPE_WEBHOOK_KEY=
+# AFFINE_SERVER_PORT=3010
+# AFFINE_SERVER_HOST=app.affine.pro
+# AFFINE_SERVER_HTTPS=true
+# DATABASE_URL="postgres://affine@localhost:5432/affine"