Fix flying strings drawing through Fog of War

[juliuss007]

Fixes a narrow part of #28.

This keeps Phobos flying text and money display strings from drawing while their map location is covered by fog or shroud. The existing helper already checks both conditions, but the draw loop did not use it, and money strings only checked shroud when they were created.

What changed:

• money strings are no longer queued when their location is fogged or shrouded
• existing flying strings are skipped while their location is fogged or shrouded
• string expiry still runs normally even while a string is hidden
• the existing public AddMoneyString interface is unchanged

Verification:

• git diff --check passed
• checked all AddMoneyString call sites; the signature is unchanged
• ran a focused static check confirming UpdateAll gates DrawText with DrawAllowed and keeps expiry cleanup

I could not run the full Phobos build in this workspace because it is macOS and the project requires Visual Studio/MSBuild with the Windows SDK. clang++ -fsyntax-only stops at the missing windows.h, and cmd.exe /c scripts\\build_debug.bat is not available here.

This is intentionally not a full Fog of War rewrite; it only addresses the flying text / money display leakage path.