perf: scan interval 50ms fixed

HL allMids pushes ~200ms, scan at 50ms catches every update
within 1 tick. Async entry goroutine means no blocking.

main.go

@@ -115,15 +115,15 @@ func main() {
 	// Main loop
 	lastHour := -1
 
-	// Random jitter 50-250ms to avoid lock-step with exchange push cycles
-	jitterMin, jitterMax := 50, 250
+	// Fixed 50ms scan interval
+	jitterMin, jitterMax := 50, 50
 	randInterval := func() time.Duration {
 		return time.Duration(jitterMin+rand.Intn(jitterMax-jitterMin+1)) * time.Millisecond
 	}
 	scannerTick := time.NewTimer(randInterval())
 	statusTick := time.NewTicker(30 * time.Second)
 
-	log.Printf("[Monitor] Scanner running every %d-%dms (random jitter)", jitterMin, jitterMax)
+	log.Printf("[Monitor] Scanner running every %dms", jitterMin)
 
 	runLoop := true
 	for runLoop {