ifcviewer: link Placement.cpp into test_federation

Commit f7add7f4 split getAxis2Placement out of an anonymous helper in
Geolocation.cpp into a shared Placement.{h,cpp}, but the test_federation
target's source list wasn't updated.  The test binary failed to link
with `undefined reference to getAxis2Placement(express::Base const&)`
from Geolocation::getWcs.  Add Placement.cpp to the explicit-source
list — it has no Qt dependency, only ifcparse.

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

src/ifcviewer/tests/CMakeLists.txt

@@ -62,9 +62,11 @@ add_executable(test_federation
     # Geolocation helpers (helmertMetersFromParameters, getWcs, getMapUnit)
     # for computeModelGeoref; compile both directly so the test doesn't
     # have to link the whole IfcViewer library (which would drag in
-    # Qt6::OpenGL, OpenCASCADE, etc.).
+    # Qt6::OpenGL, OpenCASCADE, etc.).  Placement.cpp provides
+    # getAxis2Placement, called from Geolocation::getWcs.
     ${IFCVIEWER_SRC}/Unit.cpp
     ${IFCVIEWER_SRC}/Geolocation.cpp
+    ${IFCVIEWER_SRC}/Placement.cpp
 )
 set_target_properties(test_federation PROPERTIES AUTOMOC ON)
 target_include_directories(test_federation PRIVATE ${IFCVIEWER_SRC})