#803 User Guide: 'Place Turnout/Structure from Hot Bar' pages orphaned in Doxygen page tree

[Allen D Byrne]

app/doc/hotbar.dox defines cmdTurnoutHotBar and cmdStructureHotBar as top-level \page entries (lines 79, 86) but neither is ever \subpage'd from a parent page. Doxygen therefore lists them as root-level Related Pages, which puts them at the bottom of the generated User Guide's page tree, disconnected from the Hot Bar section (cmdHotBar / hbTurnouts / hbStructures) where they belong contentwise. Both are live runtime F1 help topics (registered via AddMenuButton in cturnout.c:3245 and cstruct.c:1247), so the content itself is correct -- this is purely a page-hierarchy nesting issue. Fix: add them as \subpage entries under cmdHotBar alongside Flex-track/hbStructures/hbTurnouts.