Initial commit of Descrybe v2 without local scratch artifacts.

Drop one-shot tmp/axe scripts and agent i18n scratch so the Gitea tree is deployable.

apps/api/internal/marketing/errors.go

@@ -0,0 +1,32 @@
+package marketing
+
+import (
+	"errors"
+
+	"github.com/descrybe/descrybe-v2/apps/api/internal/feeds"
+)
+
+// clientError is a validation message safe to return to API clients.
+type clientError struct {
+	msg string
+}
+
+func (e *clientError) Error() string { return e.msg }
+
+// ClientMsg marks a message as safe to expose in HTTP 4xx responses.
+func ClientMsg(msg string) error {
+	return &clientError{msg: msg}
+}
+
+// ClientError reports whether err is a known client-facing marketing error.
+// Feed create/update validation from PrepareCampaign is also exposed.
+func ClientError(err error) (msg string, ok bool) {
+	if err == nil {
+		return "", false
+	}
+	var ce *clientError
+	if errors.As(err, &ce) {
+		return ce.msg, true
+	}
+	return feeds.ClientError(err)
+}