refactor: unify image download into a single DownloadImageCmd

DownloadImageCmd and DownloadWireguardImageCmd were identical except for
the image URL. Collapse them into one DownloadImageCmd that takes the
image as a parameter, passing imageName/wireguardImageName at the call
sites.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

internal/tui/cmds.go

@@ -43,12 +43,10 @@ func TickCmd() tea.Cmd {
 	})
 }
 
-func DownloadImageCmd(username, password string) tea.Cmd {
+func DownloadImageCmd(image, username, password string) tea.Cmd {
 	return func() tea.Msg {
-		url := imageName
-
 		loginOut, err := exec.Command(
-			"docker", "login", url,
+			"docker", "login", image,
 			"-u", username,
 			"-p", password,
 		).CombinedOutput()
@@ -60,29 +58,7 @@ func DownloadImageCmd(username, password string) tea.Cmd {
 			}
 		}
 
-		message, err := PullImage(url)
-		return ImageDownloadFinishedMsg{Message: message, Err: err}
-	}
-}
-
-func DownloadWireguardImageCmd(username, password string) tea.Cmd {
-	return func() tea.Msg {
-		url := wireguardImageName
-
-		loginOut, err := exec.Command(
-			"docker", "login", url,
-			"-u", username,
-			"-p", password,
-		).CombinedOutput()
-
-		if err != nil {
-			return ImageDownloadFinishedMsg{
-				Message: string(loginOut),
-				Err:     fmt.Errorf("falha no login: %w", err),
-			}
-		}
-
-		message, err := PullImage(url)
+		message, err := PullImage(image)
 		return ImageDownloadFinishedMsg{Message: message, Err: err}
 	}
 }