feat(app): Integrate application versioning

This commit introduces application versioning, exposing version information through the Modbus server and logging it at startup.

- Add  to provide version information
- Update  to log the application version at startup
- Update  to expose firmware version via Modbus
- Add file association for  in

software/apps/slave_node/src/main.c

@@ -4,12 +4,13 @@
 #include <lib/modbus_server.h>
 #include <lib/valve.h>
 #include <lib/fwu.h>
+#include <app_version.h>
 
 LOG_MODULE_REGISTER(main, LOG_LEVEL_INF);
 
 int main(void)
 {
-	LOG_INF("Starting Irrigation System Slave Node");
+	LOG_INF("Starting Irrigation System Slave Node version %s (Build version %s)", APP_VERSION_STRING, STRINGIFY(APP_BUILD_VERSION));
 
 	if (settings_subsys_init() || settings_load()) {
 		LOG_ERR("Settings initialization or loading failed");