Implement GPU backend detection for Blender compatibility

- Added functionality to detect GPU backends (HIP and NVIDIA) during runner registration, enhancing compatibility for Blender versions below 4.x.
- Introduced a new method, DetectAndStoreGPUBackends, to download the latest Blender and run a detection script, storing the results for future rendering decisions.
- Updated rendering logic to force CPU rendering when HIP is detected on systems with Blender < 4.x, ensuring stability and compatibility.
- Enhanced the Context structure to include flags for GPU detection status, improving error handling and rendering decisions based on GPU availability.

internal/runner/api/manager.go

@@ -442,3 +442,32 @@ func (m *ManagerClient) DownloadBlender(version string) (io.ReadCloser, error) {
 
 	return resp.Body, nil
 }
+
+// blenderVersionsResponse is the response from GET /api/blender/versions.
+type blenderVersionsResponse struct {
+	Versions []struct {
+		Full string `json:"full"`
+	} `json:"versions"`
+}
+
+// GetLatestBlenderVersion returns the latest Blender version string (e.g. "4.2.3") from the manager.
+// Uses the flat versions list which is newest-first.
+func (m *ManagerClient) GetLatestBlenderVersion() (string, error) {
+	resp, err := m.Request("GET", "/api/blender/versions", nil)
+	if err != nil {
+		return "", fmt.Errorf("failed to fetch blender versions: %w", err)
+	}
+	defer resp.Body.Close()
+	if resp.StatusCode != http.StatusOK {
+		body, _ := io.ReadAll(resp.Body)
+		return "", fmt.Errorf("blender versions returned status %d: %s", resp.StatusCode, string(body))
+	}
+	var out blenderVersionsResponse
+	if err := json.NewDecoder(resp.Body).Decode(&out); err != nil {
+		return "", fmt.Errorf("failed to decode blender versions: %w", err)
+	}
+	if len(out.Versions) == 0 {
+		return "", fmt.Errorf("no blender versions available")
+	}
+	return out.Versions[0].Full, nil
+}