Improve error messages

Author: jadolg

index.html

@@ -368,14 +368,17 @@
                     detail: null,
                 };
 
-                // Check for common error patterns
-                if (
+                // Check for common error patterns — check backend status-based
+                // messages first, then fall back to registry error codes.
+                if (errorMessage.includes("image not found")) {
+                    result.title = "Image Not Found";
+                    result.message = "The requested image does not exist.";
+                } else if (
                     errorMessage.includes("MANIFEST_UNKNOWN") ||
                     errorMessage.includes("manifest unknown")
                 ) {
                     result.title = "Image Not Found";
                     result.message = "The requested image tag does not exist.";
-                    // Try to extract the tag
                     const tagMatch = errorMessage.match(
                         /unknown tag=([^\s}"]+)/,
                     );
@@ -388,6 +391,10 @@
                 ) {
                     result.title = "Repository Not Found";
                     result.message = "The requested repository does not exist.";
+                } else if (errorMessage.includes("access denied")) {
+                    result.title = "Access Denied";
+                    result.message =
+                        "The image may not exist, or you may need credentials to access it.";
                 } else if (
                     errorMessage.includes("UNAUTHORIZED") ||
                     errorMessage.includes("unauthorized")

registry.go

@@ -237,7 +237,7 @@ func (c *RegistryClient) fetchToken(realm, service, scope string, creds Registry
 	if resp.StatusCode != http.StatusOK {
 		body, _ := io.ReadAll(io.LimitReader(resp.Body, 4096))
 		log.WithField("response_body", string(body)).WithField("status_code", resp.StatusCode).Debug("Authentication request failed")
-		return "", fmt.Errorf("authentication failed (status %d): check credentials, or the image may not exist or may be private — %s", resp.StatusCode, string(body))
+		return "", fmt.Errorf("authentication failed (status %d): check credentials or verify the image exists", resp.StatusCode)
 	}
 
 	var tokenResp struct {