Remove bufpool references and unused imports, optimize memory operations.

- Removed `bufpool` usage throughout `tag`, `tags`, and `event` packages for memory efficiency.
- Replaced in-place buffer modifications with independent, deep-copied allocations to prevent unintended mutations.
- Added new `Clone` method for deep copying `event.E`.
- Ensured valid JSON emission for nil `Tags` in `event` marshaling.
- Introduced `cmd/stresstest` for relay stress-testing with detailed workload generation and query simulation.

app/handle-event.go

@@ -151,7 +151,9 @@ func (l *Listener) HandleEvent(msg []byte) (err error) {
 		return
 	}
 	// Deliver the event to subscribers immediately after sending OK response
-	go l.publishers.Deliver(env.E)
+	// Clone the event to prevent corruption when the original is freed
+	clonedEvent := env.E.Clone()
+	go l.publishers.Deliver(clonedEvent)
 	log.D.F("saved event %0x", env.E.ID)
 	var isNewFromAdmin bool
 	for _, admin := range l.Admins {