feat(deploy): add vps deployment assets

deploy/vps/generate-jwt.sh

@@ -0,0 +1,24 @@
+#!/bin/sh
+set -eu
+
+if [ ! -f deploy/vps/.env ]; then
+    echo "Missing deploy/vps/.env"
+    exit 1
+fi
+
+JWT_PASSPHRASE=$(grep '^JWT_PASSPHRASE=' deploy/vps/.env | cut -d= -f2-)
+
+if [ -z "$JWT_PASSPHRASE" ]; then
+    echo "JWT_PASSPHRASE is empty in deploy/vps/.env"
+    exit 1
+fi
+
+mkdir -p backend/config/jwt
+
+openssl genrsa -aes256 -passout "pass:${JWT_PASSPHRASE}" -out backend/config/jwt/private.pem 4096
+openssl rsa -pubout -passin "pass:${JWT_PASSPHRASE}" -in backend/config/jwt/private.pem -out backend/config/jwt/public.pem
+
+chmod 600 backend/config/jwt/private.pem
+chmod 644 backend/config/jwt/public.pem
+
+echo "JWT keypair generated in backend/config/jwt"