fix locale-dependent std::stod fallback in Any and SwitchNode

[aysha-afrah26]

On toolchains without the floating-point std::from_chars overload, which is the case for Apple libc++ and therefore the macOS CI job, Any::stringToNumber and the real-number comparison in CheckStringEquality fall back to std::stod. That call honors LC_NUMERIC, so as soon as the host application selects a locale that uses a comma as decimal separator (Qt and GTK programs call setlocale(LC_ALL, "") at startup) the string "3.5" comes back as 3 with the fraction silently dropped, because strtod stops at the dot and the fallback treats that as success. Every string to number conversion that goes through Any is affected: Blackboard::get on a string entry, script comparisons and assignments that mix a string variable with a number, and Switch case routing, where variable="3.50" case_1="3.5" ends up in the default child. I noticed it while reading the from_chars fallbacks after #1167 and reproduced it on macOS with a de_DE thread locale set through uselocale(). Since #1167 the library already has a locale-independent BT::parseDouble that mirrors std::from_chars, so the fix routes both remaining fallbacks through it (prefix semantics in Any, full-string in the switch comparison, exactly like their from_chars branches) instead of keeping a second parsing convention around. The only header change is a forward declaration in safe_any.hpp, because basic_types.h includes that header and not the other way round; Any::stringToNumber is an inline template and the exported signature of CheckStringEquality is unchanged, so there is no ABI impact. The two regression tests switch only the calling thread to a comma-decimal locale and skip when the machine does not have one, so they fail before and pass after on macOS and stay green on Linux and Windows, where from_chars is used.