extract loadShips into ConfigLoaderShips.cpp

Continues the ConfigLoader.cpp domain split. parseRotationString and
parsePlacedModules are only used by loadShips, so they move along as
domain-local anonymous-namespace helpers rather than into TomlHelpers.
Pure move; no logic change.

Co-Authored-By: Claude <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01YHcUerKAZKWNvSKJxYKbnG

src/lib/config/CMakeLists.txt

@@ -24,6 +24,7 @@ SET(SRCS
     ${CMAKE_CURRENT_SOURCE_DIR}/ConfigLoaderWorld.cpp
     ${CMAKE_CURRENT_SOURCE_DIR}/ConfigLoaderBuildings.cpp
     ${CMAKE_CURRENT_SOURCE_DIR}/ConfigLoaderRecipes.cpp
+    ${CMAKE_CURRENT_SOURCE_DIR}/ConfigLoaderShips.cpp
     ${CMAKE_CURRENT_SOURCE_DIR}/SurfaceMask.cpp
     ${CMAKE_CURRENT_SOURCE_DIR}/BlueprintSerializer.cpp
     ${CMAKE_CURRENT_SOURCE_DIR}/ShipLayoutBlueprintSerializer.cpp