ax(mining): remove banned fmt import from version.go

Replace fmt.Errorf with ErrInternal().WithCause() and
fmt.Sprintf URL with string concatenation + strconv.Itoa.

Co-Authored-By: Charon <charon@lethean.io>

pkg/mining/version.go

@@ -2,9 +2,9 @@ package mining
 
 import (
 	"encoding/json"
-	"fmt"
 	"io"
 	"net/http"
+	"strconv"
 )
 
 var (
@@ -50,14 +50,14 @@ func FetchLatestGitHubVersion(owner, repo string) (string, error) {
 					return tagName, nil
 				}
 			}
-			return "", fmt.Errorf("github API unavailable (circuit breaker open): %w", err)
+			return "", ErrInternal("github API unavailable (circuit breaker open)").WithCause(err)
 		}
 		return "", err
 	}
 
 	tagName, ok := result.(string)
 	if !ok {
-		return "", fmt.Errorf("unexpected result type from circuit breaker")
+		return "", ErrInternal("unexpected result type from circuit breaker")
 	}
 
 	return tagName, nil
@@ -65,22 +65,22 @@ func FetchLatestGitHubVersion(owner, repo string) (string, error) {
 
 // tag, err := fetchGitHubVersionDirect("xmrig", "xmrig") // "v6.21.0"; called via circuit breaker
 func fetchGitHubVersionDirect(owner, repo string) (string, error) {
-	url := fmt.Sprintf("https://api.github.com/repos/%s/%s/releases/latest", owner, repo)
+	url := "https://api.github.com/repos/" + owner + "/" + repo + "/releases/latest"
 
 	resp, err := getHTTPClient().Get(url)
 	if err != nil {
-		return "", fmt.Errorf("failed to fetch version: %w", err)
+		return "", ErrInternal("failed to fetch version").WithCause(err)
 	}
 	defer resp.Body.Close()
 
 	if resp.StatusCode != http.StatusOK {
 		io.Copy(io.Discard, resp.Body) // Drain body to allow connection reuse
-		return "", fmt.Errorf("failed to get latest release: unexpected status code %d", resp.StatusCode)
+		return "", ErrInternal("failed to get latest release: unexpected status code " + strconv.Itoa(resp.StatusCode))
 	}
 
 	var release GitHubRelease
 	if err := json.NewDecoder(resp.Body).Decode(&release); err != nil {
-		return "", fmt.Errorf("failed to decode release: %w", err)
+		return "", ErrInternal("failed to decode release").WithCause(err)
 	}
 
 	return release.TagName, nil