Use mcdsl/terminal.ReadPassword for secure password input

Replaces raw bufio.Scanner password reading (which echoed to terminal)
with the new mcdsl terminal package that suppresses echo via x/term.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

cmd/mcp/login.go

@@ -8,6 +8,7 @@ import (
 
 	"github.com/spf13/cobra"
 
+	"git.wntrmute.dev/mc/mcdsl/terminal"
 	"git.wntrmute.dev/mc/mcp/internal/auth"
 	"git.wntrmute.dev/mc/mcp/internal/config"
 )
@@ -33,14 +34,11 @@ func loginCmd() *cobra.Command {
 			}
 			username := strings.TrimSpace(scanner.Text())
 
-			fmt.Print("Password: ")
-			if !scanner.Scan() {
-				if err := scanner.Err(); err != nil {
-					return fmt.Errorf("read password: %w", err)
-				}
-				return fmt.Errorf("read password: unexpected end of input")
+			password, err := terminal.ReadPassword("Password: ")
+			if err != nil {
+				return fmt.Errorf("read password: %w", err)
 			}
-			password := strings.TrimSpace(scanner.Text())
+			password = strings.TrimSpace(password)
 
 			token, err := auth.Login(cfg.MCIAS.ServerURL, cfg.MCIAS.CACert, username, password)
 			if err != nil {