feat(installer): add TLS and monitoring overlay templates

Optional compose overlays: TLS overlay mounts user-supplied certs into
traefik, monitoring overlay replaces the noop bridge with an external
Docker network for Prometheus scraping.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

installer/templates/docker-compose.monitoring.yml

@@ -0,0 +1,7 @@
+# External monitoring network overlay
+# Overrides the noop monitoring bridge with a real external network
+
+networks:
+  monitoring:
+    external: true
+    name: ${MONITORING_NETWORK:?MONITORING_NETWORK must be set in .env}

installer/templates/docker-compose.tls.yml

@@ -0,0 +1,7 @@
+# Custom TLS certificates overlay
+# Adds user-supplied certificate volume to traefik
+
+services:
+  cameleer-traefik:
+    volumes:
+      - ./certs:/user-certs:ro