refactor(slave_node): Clean up initial configuration

- Remove redundant DTS_ROOT from CMakeLists.txt as it's inferred from BOARD_ROOT.
- Clear the project configuration (prj.conf) to start with a minimal baseline.

software/apps/slave_node/CMakeLists.txt

@@ -2,9 +2,8 @@ cmake_minimum_required(VERSION 3.20)
 
 # Point BOARD_ROOT and DTS_ROOT to the 'software' directory, which contains 'boards'.
 list(APPEND BOARD_ROOT ${CMAKE_CURRENT_SOURCE_DIR}/../..)
-list(APPEND DTS_ROOT ${CMAKE_CURRENT_SOURCE_DIR}/../..)
 
 find_package(Zephyr REQUIRED HINTS $ENV{ZEPHYR_BASE})
 project(slave_node)
 
-target_sources(app PRIVATE src/main.c)
+target_sources(app PRIVATE src/main.c)