fix(build): migrate project config to .smartconfig.json and replace smartfile usage with native fs

ts_destination_buffer/classes.destinationbuffer.ts

@@ -46,8 +46,9 @@ export class SmartlogDestinationBuffer implements ILogDestination {
     }
 
     // Filter by timestamp
-    if (options?.since) {
-      results = results.filter((pkg) => pkg.timestamp >= options.since);
+    if (options?.since !== undefined) {
+      const since = options.since;
+      results = results.filter((pkg) => pkg.timestamp >= since);
     }
 
     // Return most recent `limit` entries in chronological order (oldest-first)