feat: allow production provider bootstrap

backend/internal/jobs/provider_test.go

@@ -40,6 +40,23 @@ func TestProviderJobBuilderPreparesImageRequestAndEngineOverride(t *testing.T) {
 	}
 }
 
+func TestProviderJobBuilderRejectsUnconfiguredProviderBeforeCreation(t *testing.T) {
+	b := testProviderBuilder()
+	b.UnavailableProviders = map[string]string{
+		"evolink": "EvoLink 服务商未配置，请先配置 EVOLINK_API_KEY。",
+	}
+	_, err := b.Build(context.Background(), "owner", "client", "image.generate", "idem", map[string]any{
+		"engine": "evolink", "prompt": "hello",
+	})
+	if err == nil || err.Error() != "EvoLink 服务商未配置，请先配置 EVOLINK_API_KEY。" {
+		t.Fatalf("error = %v", err)
+	}
+	var unavailable *Error
+	if !errors.As(err, &unavailable) || unavailable.Kind != ErrorUnavailable || unavailable.Status != 503 {
+		t.Fatalf("error = %#v, want unavailable 503", err)
+	}
+}
+
 func TestProviderJobBuilderUsesPublicInputURLsForImageMaterialCoverage(t *testing.T) {
 	b := testProviderBuilder()
 	cmd, err := b.Build(context.Background(), "owner", "client", "image.generate", "", map[string]any{