Add SSH-managed node registry with connection testing and reauth.

Register hosts under Containers/VMs/Docker with encrypted key storage, and require re-authentication for sensitive account changes.

service/internal/auth/uuid.go

@@ -0,0 +1,24 @@
+package auth
+
+import (
+	"crypto/rand"
+	"fmt"
+)
+
+// NewUUID returns a random RFC 4122 version-4 UUID string.
+func NewUUID() (string, error) {
+	buffer := make([]byte, 16)
+	if _, err := rand.Read(buffer); err != nil {
+		return "", fmt.Errorf("uuid: %w", err)
+	}
+	buffer[6] = (buffer[6] & 0x0f) | 0x40
+	buffer[8] = (buffer[8] & 0x3f) | 0x80
+	return fmt.Sprintf(
+		"%x-%x-%x-%x-%x",
+		buffer[0:4],
+		buffer[4:6],
+		buffer[6:8],
+		buffer[8:10],
+		buffer[10:16],
+	), nil
+}