feat(log): introdueix Log:: wrapper sobre SDL_Log

Logger lleuger a source/utils/log.{hpp,cpp} amb API basada en std::format
i filtre runtime via la variable d'entorn AEE_LOG (sintaxi
*:info,Resource::Helper:warn,scene:debug). Substitueix gradualment els
std::cout/cerr dispersos.

- Categories CUSTOM registrades sota demanda; per defecte INFO.
- Categories SDL natives no es toquen tret que l'usuari posi *:level.
- Migra resource_helper.cpp i els marcadors d'inici/fi (main.cpp) com a
  testimoni; la resta de subsistemes es migra en commits següents.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

CMakeLists.txt

@@ -104,6 +104,7 @@ set(APP_SOURCES
     source/core/resources/resource_pack.cpp
     source/core/resources/palette_loader.cpp
     source/utils/easing.cpp
+    source/utils/log.cpp
     source/utils/utils.cpp
     source/game/debug_config.cpp
     source/game/options.cpp
@@ -365,6 +366,7 @@ if(BUILD_TESTS)
         source/core/resources/resource_helper.cpp
         source/core/resources/resource_pack.cpp
         source/game/map/map.cpp
+        source/utils/log.cpp
         ${ENTITY_SOURCES_BASE}
     )
     target_include_directories(test_entities_smoke PRIVATE
@@ -394,6 +396,7 @@ if(BUILD_TESTS)
         source/core/resources/resource_helper.cpp
         source/core/resources/resource_pack.cpp
         source/game/map/map.cpp
+        source/utils/log.cpp
         ${ENTITY_SOURCES_BASE}
         source/game/entities/concrete/whip_attack.cpp
     )
@@ -418,6 +421,7 @@ if(BUILD_TESTS)
         source/core/input/key_config.cpp
         source/core/resources/resource_helper.cpp
         source/core/resources/resource_pack.cpp
+        source/utils/log.cpp
     )
     target_include_directories(test_scene_flow PRIVATE
         "${CMAKE_SOURCE_DIR}/source"
@@ -457,6 +461,7 @@ if(BUILD_TESTS)
         source/core/resources/resource_helper.cpp
         source/core/resources/resource_pack.cpp
         source/utils/easing.cpp
+        source/utils/log.cpp
     )
     target_include_directories(test_game_fsm PRIVATE
         "${CMAKE_SOURCE_DIR}/source"