Add node mode with SSH auto-install and Remnawave-style manual deploy.

Co-authored-by: Cursor <cursoragent@cursor.com>

internal/secretbox/secretbox.go

@@ -0,0 +1,71 @@
+package secretbox
+
+import (
+	"crypto/aes"
+	"crypto/cipher"
+	"crypto/rand"
+	"crypto/sha256"
+	"encoding/base64"
+	"errors"
+	"io"
+)
+
+func DeriveKey(secret string) []byte {
+	sum := sha256.Sum256([]byte(secret))
+	return sum[:]
+}
+
+func Encrypt(key []byte, plaintext string) (string, error) {
+	if plaintext == "" {
+		return "", nil
+	}
+	block, err := aes.NewCipher(key)
+	if err != nil {
+		return "", err
+	}
+	gcm, err := cipher.NewGCM(block)
+	if err != nil {
+		return "", err
+	}
+	nonce := make([]byte, gcm.NonceSize())
+	if _, err := io.ReadFull(rand.Reader, nonce); err != nil {
+		return "", err
+	}
+	out := gcm.Seal(nonce, nonce, []byte(plaintext), nil)
+	return base64.StdEncoding.EncodeToString(out), nil
+}
+
+func Decrypt(key []byte, encoded string) (string, error) {
+	if encoded == "" {
+		return "", nil
+	}
+	raw, err := base64.StdEncoding.DecodeString(encoded)
+	if err != nil {
+		return "", err
+	}
+	block, err := aes.NewCipher(key)
+	if err != nil {
+		return "", err
+	}
+	gcm, err := cipher.NewGCM(block)
+	if err != nil {
+		return "", err
+	}
+	if len(raw) < gcm.NonceSize() {
+		return "", errors.New("ciphertext too short")
+	}
+	nonce, ciphertext := raw[:gcm.NonceSize()], raw[gcm.NonceSize():]
+	plain, err := gcm.Open(nil, nonce, ciphertext, nil)
+	if err != nil {
+		return "", err
+	}
+	return string(plain), nil
+}
+
+func RandomToken(n int) (string, error) {
+	b := make([]byte, n)
+	if _, err := io.ReadFull(rand.Reader, b); err != nil {
+		return "", err
+	}
+	return base64.RawURLEncoding.EncodeToString(b), nil
+}