tests(model): Fix CMakeLists syntax and SPDX headers

Correct target_sources syntax to use openpfc-tests and
add test_model_fft_baseline.cpp. Normalize SPDX headers.

Author: ahojukka5

tests/unit/models/CMakeLists.txt

@@ -1,10 +1,9 @@
-#SPDX - FileCopyrightText : 2025 VTT Technical Research Centre of Finland Ltd
-#SPDX - License - Identifier : AGPL - 3.0 - or -later
+# SPDX-FileCopyrightText: 2025 VTT Technical Research Centre of Finland Ltd
+# SPDX-License-Identifier: AGPL-3.0-or-later
 
-#Model unit tests
-target_sources(openpfc - tests PRIVATE ${CMAKE_CURRENT_SOURCE_DIR} /
-                             test_model.cpp ${CMAKE_CURRENT_SOURCE_DIR} /
-                             test_model_fft_baseline.cpp
-#${CMAKE_CURRENT_SOURCE_DIR } /                                                     \
-   test_model_comprehensive.cpp #TODO : Fix incomplete test
+# Model unit tests
+target_sources(openpfc-tests PRIVATE
+    ${CMAKE_CURRENT_SOURCE_DIR}/test_model.cpp
+    ${CMAKE_CURRENT_SOURCE_DIR}/test_model_fft_baseline.cpp
+    # ${CMAKE_CURRENT_SOURCE_DIR}/test_model_comprehensive.cpp  # TODO: Fix incomplete test
 )