PackageRecommendations: Add distribution to package recommendations

- Add required distribution field to RecommendPackageRequest
- Add modelVersion field to RecommendationsResponse
- Update frontend to send RHEL major version to API
- Add analytics tracking for distribution and modelVersion

Enables version-specific package recommendations and model usage tracking.

api/schema/imageBuilder.yaml

@@ -1567,6 +1567,10 @@ components:
           type: integer
           format: int32
           default: 3
+        distribution:
+          type: string
+          description: RHEL major release (e.g. "rhel8", "rhel9", "rhel10")
+          example: "rhel9"
     RecommendationsResponse:
       required:
         - packages
@@ -1576,6 +1580,10 @@ components:
           type: array
           items:
             type: string
+        modelVersion:
+          type: string
+          description: Version of the recommendation model used
+          example: "rpm_rex_42"
     ClonesResponse:
       required:
         - meta