fix(logging): scope logRotator state per instance

`lastRotationTime` and `setIntervalId` were module-level. After #1111
fixed the broken require so harper_logger.getFileLogger actually
creates rotators, multiple rotators can exist concurrently (e.g. for
http logger, external logger, hdb logger). Every new rotator call
overwrites the shared `setIntervalId`, so `rotator.end()` on any
instance clears the most-recently-created interval — not its own.

This surfaced as a unit-test regression: the harper_logger HTTP and
global-logger tests trigger lingering setTimeouts (from the
`path =` setter calling getFileLogger) that fire ~100ms later. When
the logRotator test then created its rotator, the lingering
setTimeouts called `logger.rotator?.end()` -> `clearInterval(module-level setIntervalId)`,
which clobbered the test's interval. The rotation never fired and
`getLastRotatedLogPath()` returned undefined.

Move both variables into the function closure so each rotator owns
its own state and `end()` only clears its own interval.

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

Author: kriszyp

utility/logging/logRotator.ts

@@ -18,9 +18,6 @@ const LOG_AUDIT_INTERVAL = 60000;
 const INT_SIZE_UNDEFINED_MSG =
 	"'interval' and 'maxSize' are both undefined, to enable logging rotation at least one of these values must be defined in harperdb-config.yaml";
 
-let lastRotationTime;
-let setIntervalId;
-
 export { logRotator };
 
 /**
@@ -67,9 +64,9 @@ function logRotator({ logger, maxSize, interval, retention, enabled, path: rotat
 
 	let lastRotatedLogPath;
 	// convert date.now to minutes
-	lastRotationTime = Date.now();
+	let lastRotationTime = Date.now();
 	hdbLogger.trace('Log rotate enabled, maxSize:', maxSize, 'interval:', interval);
-	setIntervalId = setInterval(async () => {
+	const setIntervalId = setInterval(async () => {
 		if (maxBytes) {
 			let fileStats;
 			try {