handle onboarding (set name)

internal/validation/name.go

@@ -0,0 +1,20 @@
+package validation
+
+import (
+	"errors"
+	"strings"
+)
+
+func ValidateName(name string) error {
+	trimmed := strings.TrimSpace(name)
+
+	if trimmed == "" {
+		return errors.New("name is required")
+	}
+
+	if len(trimmed) > 100 {
+		return errors.New("name is too long (max 100 characters)")
+	}
+
+	return nil
+}