fix(posix): initialize PX4 before starting the daemon server

The daemon server's client-handler thread spawns module tasks (e.g. dataman).
Start px4::init_once()/init() before creating px4_daemon::Server so platform init
- uORB, work queues, logging - completes with a happens-before edge to those
tasks. Otherwise a module task racing the still-running init reads globals like
uORB::Manager's instance pointer or the log message advertisement without
synchronization (ThreadSanitizer flags it) - and an atomic would not make it
correct, since the publication could simply be skipped.

platforms/posix/src/px4/common/main.cpp

@@ -368,18 +368,23 @@ int main(int argc, char **argv)
 		register_sig_handler();
 		set_cpu_scaling();
 
-		px4_daemon::Server server(instance);
-		server.start();
-
 		ret = create_dirs();
 
 		if (ret != PX4_OK) {
 			return ret;
 		}
 
+		// Initialize PX4 (uORB, work queues, logging, ...) before starting the
+		// daemon server. The server's client-handler thread spawns module tasks
+		// (e.g. dataman), so platform init must happen-before that thread is
+		// created. Otherwise those tasks race on globals such as the uORB::Manager
+		// instance pointer and the log message advertisement.
 		px4::init_once();
 		px4::init(argc, argv, "px4");
 
+		px4_daemon::Server server(instance);
+		server.start();
+
 		// Don't set this up until PX4 is up and running
 		ret = set_server_running(instance);