[Android:Bugfix] Add missing diffusion_session and sana_session sources to CMakeLists (#4569)

diffusion_jni.cpp and sana_jni.cpp depend on DiffusionSession and
SanaSession classes defined in diffusion_session.cpp and
sana_session.cpp, but these source files were missing from
CMakeLists.txt, causing UnsatisfiedLinkError at runtime.

Co-authored-by: Claude Fable 5 <noreply@anthropic.com>

apps/Android/MnnLlmChat/app/src/main/cpp/CMakeLists.txt

@@ -30,6 +30,10 @@ add_library(${CMAKE_PROJECT_NAME} SHARED
         llm_session.cpp
         crash_util.cpp
         processor.cpp
+        diffusion_jni.cpp
+        diffusion_session.cpp
+        sana_jni.cpp
+        sana_session.cpp
         # Video processing files (moved to video/ directory)
         video/video_decoder.cpp
         video/byte_buffer_decoder.cpp