feat(observability): add SearXNG, Argos, and Pallas monitoring

- Add SearXNG syslog ingestion and blackbox health probes on miranda
  and rosalind for per-host attributable failure detection
- Scrape Argos MCP application metrics from miranda
- Add Pallas dashboard panels for downstream availability and turn
  error ratios

ansible/neo4j_mcp/docker-compose.yml.j2

@@ -1,7 +1,7 @@
+# Generated by Ansible - do not edit manually
 services:
   neo4j-cypher:
-    image: mcp/neo4j-cypher:latest
-    pull_policy: always
+    image: mcp/neo4j-cypher:{{ neo4j_mcp_image_version }}
     container_name: neo4j-cypher
     restart: unless-stopped
     ports:
@@ -9,14 +9,14 @@ services:
     environment:
       - NEO4J_URI=bolt://{{neo4j_host}}:{{neo4j_bolt_port}}
       - NEO4J_USERNAME=neo4j
-      - NEO4J_PASSWORD={{neo4j_auth_password}}
+      - NEO4J_PASSWORD={{neo4j_cypher_password}}
       - NEO4J_DATABASE=neo4j
       - NEO4J_TRANSPORT=http
       - NEO4J_MCP_SERVER_HOST=0.0.0.0
       - NEO4J_MCP_SERVER_PORT=8000
       - NEO4J_MCP_SERVER_PATH=/mcp
       - NEO4J_NAMESPACE=local
-      - NEO4J_MCP_SERVER_ALLOWED_HOSTS=localhost,127.0.0.1,miranda.incus,rosalind.incus,miranda.incus:{{neo4j_cypher_mcp_port}}
+      - NEO4J_MCP_SERVER_ALLOWED_HOSTS={{neo4j_mcp_server_allowed_hosts}}
       - NEO4J_MCP_SERVER_ALLOW_ORIGINS=
       - NEO4J_READ_TIMEOUT=30
     logging: