Bump mcdsl to v1.6.0 (SSO redirect fix)

Fixes SSO login redirect loop where the return-to cookie stored
/sso/redirect, bouncing users back to MCIAS after successful login.

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

vendor/git.wntrmute.dev/mc/mcdsl/sso/sso.go

@@ -229,7 +229,7 @@ func ValidateStateCookie(w http.ResponseWriter, r *http.Request, prefix, querySt
 // redirect back to it after SSO login completes.
 func SetReturnToCookie(w http.ResponseWriter, r *http.Request, prefix string) {
 	path := r.URL.Path
-	if path == "" || path == "/login" || path == "/sso/callback" {
+	if path == "" || path == "/login" || strings.HasPrefix(path, "/sso/") {
 		path = "/"
 	}
 	http.SetCookie(w, &http.Cookie{

vendor/modules.txt

@@ -1,4 +1,4 @@
-# git.wntrmute.dev/mc/mcdsl v1.5.0
+# git.wntrmute.dev/mc/mcdsl v1.6.0
 ## explicit; go 1.25.7
 git.wntrmute.dev/mc/mcdsl/auth
 git.wntrmute.dev/mc/mcdsl/config