refactor: use english for routes, parameters and internal messages

templates/board/_floorplan.html.twig

@@ -4,8 +4,8 @@
     partial there and nothing else.
 
     Colouring needs no JavaScript at all: the plan is re-rendered server side for the selected day
-    and span, so free/belegt/deine is decided in Twig. Note "free" is always relative to the span
-    in the header -- a desk booked 09:00-13:00 is free for an afternoon board and belegt for an
+    and span, so free/taken/yours is decided in Twig. Note "free" is always relative to the span
+    in the header -- a desk booked 09:00-13:00 is free for an afternoon board and taken for an
     all-day one.
 #}
 <div class="rounded-md border border-gray-200 p-4">