fix: use execvp instead of system() for privilege escalation

system() blocked and prevented pkexec from re-launching the program.
execvp replaces the process, allowing pkexec to take over properly.

src/main.cpp

@@ -6,6 +6,7 @@
 #include <ctime>
 #include <fstream>
 #include <string>
+#include <vector>
 #include <unistd.h>
 #include "config.h"
 #include "rsync_manager.h"
@@ -24,16 +25,17 @@ static void escalate_privileges(int argc, char* argv[]) {
 
 	g_print("x3-backup requires root privileges. Re-launching with pkexec...\n");
 
-	std::string cmd = "pkexec";
-	for (int i = 0; i < argc; i++) {
-		std::string arg = argv[i];
-		if (arg.find(' ') != std::string::npos)
-			cmd += " \"" + arg + "\"";
-		else
-			cmd += " " + arg;
-	}
-	int ret = system(cmd.c_str());
-	exit(ret);
+	/* Build argv for exec: pkexec + original args + NULL */
+	std::vector<const char*> new_argv;
+	new_argv.push_back("pkexec");
+	for (int i = 0; i < argc; i++)
+		new_argv.push_back(argv[i]);
+	new_argv.push_back(nullptr);
+
+	execvp("pkexec", const_cast<char* const*>(new_argv.data()));
+	/* If execvp returns, it failed */
+	perror("execvp pkexec");
+	exit(1);
 }
 
 static std::string get_log_path() {