fix: registry test endpoint accepts empty body for connectivity check

internal/api/registries.go

@@ -180,14 +180,12 @@ func (s *Server) testRegistry(w http.ResponseWriter, r *http.Request) {
 		return
 	}
 
+	// Body is optional — if no image provided, just test connectivity.
 	var req testRegistryRequest
-	if !decodeJSON(w, r, &req) {
-		return
-	}
-
-	if req.Image == "" {
-		respondError(w, http.StatusBadRequest, "image is required for testing")
-		return
+	if r.Body != nil && r.ContentLength > 0 {
+		if !decodeJSON(w, r, &req) {
+			return
+		}
 	}
 
 	// Decrypt the token.
@@ -207,6 +205,14 @@ func (s *Server) testRegistry(w http.ResponseWriter, r *http.Request) {
 		return
 	}
 
+	// If no image provided, just verify we can create a client (basic connectivity test).
+	if req.Image == "" {
+		respondJSON(w, http.StatusOK, map[string]any{
+			"message": "registry client created successfully",
+		})
+		return
+	}
+
 	tags, err := client.ListTags(r.Context(), req.Image)
 	if err != nil {
 		respondError(w, http.StatusBadGateway, "registry test failed: "+err.Error())