Fix more Valgrind uninitialized value errors

1. MySQL_Logger.cpp: Initialize username_len, schemaname_len, and server_len
   to 0 in MySQL_Event constructor. These fields were uninitialized and
   used in copy constructor and JSON serialization.

2. debug.cpp: Add default member initializers to DebugLogEntry struct
   to ensure POD fields are zero-initialized. Move errno save/restore
   to after early return checks to avoid potential TLS access issues
   before thread is fully initialized.

lib/MySQL_Logger.cpp

@@ -353,6 +353,8 @@ MySQL_Event::MySQL_Event (log_event_type _et, uint32_t _thread_id, char * _usern
 	thread_id=_thread_id;
 	username=_username;
 	schemaname=_schemaname;
+	username_len=0;
+	schemaname_len=0;
 	start_time=_start_time;
 	end_time=_end_time;
 	query_digest=_query_digest;
@@ -361,6 +363,7 @@ MySQL_Event::MySQL_Event (log_event_type _et, uint32_t _thread_id, char * _usern
 	et=_et;
 	hid=UINT64_MAX;
 	server=NULL;
+	server_len=0;
 	extra_info = NULL;
 	have_affected_rows=false;
 	affected_rows=0;

lib/debug.cpp

@@ -31,15 +31,15 @@ static unsigned int debug_output = 1;
 
 
 struct DebugLogEntry {
-	unsigned long long time;
-	unsigned long long lapse;
-	int thr;
+	unsigned long long time = 0;
+	unsigned long long lapse = 0;
+	int thr = 0;
 	std::string file;
-	int line;
+	int line = 0;
 	std::string funct;
-	int module;
+	int module = 0;
 	std::string modname;
-	int verbosity;
+	int verbosity = 0;
 	std::string message;
 	std::string backtrace;
 };
@@ -178,20 +178,19 @@ void proxy_debug_func(
 	const char *fmt,
 	...
 ) {
-	int saved_errno = errno;
 	assert(module<PROXY_DEBUG_UNKNOWN);
 	// Safety check: ensure debug struct is initialized
 	if (GloVars.global.gdbg_lvl == NULL) {
-		errno = saved_errno;
 		return;
 	}
 	if (pretime == 0) { // never initialized
 		pretime=realtime_time();
 	}
 	if (GloVars.global.gdbg_lvl[module].verbosity < verbosity) {
-		errno = saved_errno;
 		return;
 	}
+	// Save errno only after passing early return checks
+	int saved_errno = errno;
 	// check if the entry must be filtered
 	if (filter_debug_entry(__file, __line, __func)) {
 		errno = saved_errno;