chore: update project references and add Citron copyright

- Replaced all references to the old project name with Citron.
- Added Citron copyright information alongside existing notices in all files.

src/core/CMakeLists.txt

@@ -1,4 +1,4 @@
-# SPDX-FileCopyrightText: 2018 yuzu Emulator Project
+# SPDX-FileCopyrightText: 2018 yuzu Emulator Project & 2025 citron Homebrew Project
 # SPDX-License-Identifier: GPL-2.0-or-later
 
 add_library(core STATIC
@@ -1233,11 +1233,11 @@ else()
         hle/service/ssl/ssl_backend_none.cpp)
 endif()
 
-if (YUZU_USE_PRECOMPILED_HEADERS)
+if (CITRON_USE_PRECOMPILED_HEADERS)
     target_precompile_headers(core PRIVATE precompiled_headers.h)
 endif()
 
-if (YUZU_ENABLE_LTO)
+if (CITRON_ENABLE_LTO)
   set_property(TARGET core PROPERTY INTERPROCEDURAL_OPTIMIZATION TRUE)
 endif()