Add Prometheus instrumentation to Normalizer, Queue, Chaos, GameServer, Broadcaster

[justintulloch]

• In each service’s main.go, call a metrics.Register…Metrics() and metrics.StartMetricsServer(":910X").

• Define and register relevant counters/gauges/histograms in internal/metrics/prometheus.go.

• Examples:

– normalizer_events_received_total (counter)

– normalizer_events_dropped_late_total (counter)

– chaos_packets_dropped_total (counter)

– queue_input_queue_depth{matchID} (gauge)

– gameserver_tick_duration_ms_bucket (histogram)

– broadcaster_packets_sent_total (counter)

• Write a short README section showing how to scrape each endpoint.