fix: use SYS: prefix in pino-pretty translateTime to honour TZ env var

pino-pretty's translateTime: "HH:MM:ss" formats all timestamps in UTC,
ignoring the process TZ environment variable. Changing the prefix to
"SYS:HH:MM:ss" instructs pino-pretty to format timestamps in the local
system timezone, so operators running in non-UTC zones see correct
wall-clock times in both the console and the server.log file.

Fixes: #2879

server/src/middleware/logger.ts

@@ -21,7 +21,7 @@ fs.mkdirSync(logDir, { recursive: true });
 const logFile = path.join(logDir, "server.log");
 
 const sharedOpts = {
-  translateTime: "HH:MM:ss",
+  translateTime: "SYS:HH:MM:ss",
   ignore: "pid,hostname",
   singleLine: true,
 };