fix(#248): mode-aware delete button text in TagDeleteGuard and fix document.querySelector in spec

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

frontend/messages/de.json

@@ -604,6 +604,7 @@
 	"admin_tag_delete_only_this_sub_root": "Untergeordnete werden zu Root-Schlagwörtern",
 	"admin_tag_delete_subtree": "Gesamten Teilbaum löschen",
 	"admin_tag_delete_subtree_warn": "Löscht auch {count} untergeordnete Schlagwörter",
+	"admin_tag_delete_subtree_confirm_btn": "Teilbaum löschen",
 	"admin_tag_delete_confirm_heading": "Gib «{name}» zur Bestätigung ein:",
 	"filter_operator_and": "UND",
 	"filter_operator_or": "ODER",

frontend/messages/en.json

@@ -604,6 +604,7 @@
 	"admin_tag_delete_only_this_sub_root": "Children will become root tags",
 	"admin_tag_delete_subtree": "Delete entire subtree",
 	"admin_tag_delete_subtree_warn": "Also deletes {count} child tags",
+	"admin_tag_delete_subtree_confirm_btn": "Delete subtree",
 	"admin_tag_delete_confirm_heading": "Type «{name}» to confirm:",
 	"filter_operator_and": "AND",
 	"filter_operator_or": "OR",

frontend/messages/es.json

@@ -604,6 +604,7 @@
 	"admin_tag_delete_only_this_sub_root": "Las subordinadas se convertirán en etiquetas raíz",
 	"admin_tag_delete_subtree": "Eliminar todo el subárbol",
 	"admin_tag_delete_subtree_warn": "También elimina {count} etiquetas subordinadas",
+	"admin_tag_delete_subtree_confirm_btn": "Eliminar subárbol",
 	"admin_tag_delete_confirm_heading": "Escribe «{name}» para confirmar:",
 	"filter_operator_and": "Y",
 	"filter_operator_or": "O",