Enable Draupnir web server (abuse reporting) and add healthz config to repo

- draupnir/production.yaml: Add health.healthz (port 8081) and web.abuseReporting
  (port 8080) config — healthz was live on LXC but missing from repo; web server
  enables Matrix client Report button forwarding to management room (Synapse module
  install on LXC 151 still needed to complete the integration)
- README: Add Draupnir port map, abuse reporting setup docs, updated monitoring
  section (3 new Prometheus scrape jobs, Draupnir Down alert, Grafana panel count),
  add presence-disabled federation lag fix to performance checklist, document
  Draupnir healthz/audit DB paths

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

draupnir/production.yaml

@@ -41,3 +41,24 @@ backgroundDelayMS: 500
 
 # Safe redaction limit per sync
 redactionLimit: 100
+
+# Health check endpoint (Prometheus scrape via blackbox exporter)
+health:
+  healthz:
+    enabled: true
+    port: 8081
+    address: "0.0.0.0"
+    endpoint: "/healthz"
+    healthyStatus: 200
+    unhealthyStatus: 418
+
+# Web server for abuse report forwarding
+# Endpoint: POST /_matrix/draupnir/1/report/{roomId}/{eventId}
+# Synapse integration: configure homeserver.yaml with the draupnir_abuse_reports module
+# (see README for setup instructions)
+web:
+  enabled: true
+  address: "0.0.0.0"
+  port: 8080
+  abuseReporting:
+    enabled: true