feat(ansible): standardize Neo4j ports and add monitoring

- Unify Neo4j HTTP/Bolt/syslog ports across ariel and umbriel hosts
- Add neo4j_metrics_port (22094) for APOC exporter sidecar
- Add umbriel to Prometheus node_exporter targets
- Add Neo4j scrape config and alerts for tx rollback rate and
  stalled store growth
- Replace kernos_harper MCP with andromeda (caliban.helu.ca)
- Remove angelia MCP from kottos fastagent config
- Switch neo4j group membership from keeper_user to ponos

ansible/pplg/prometheus.yml.j2

@@ -62,4 +62,17 @@ scrape_configs:
     metrics_path: '/metrics'
     scrape_interval: 15s
 
+  # Neo4j — stscoundrel/neo4j-apoc-exporter sidecar connects to the local
+  # Neo4j over Bolt and exposes apoc.monitor.* (tx/ids/store) plus JVM
+  # metrics on the standard metrics port (22094).  Both Ariel (LLM memory
+  # via neo4j-cypher MCP) and Umbriel (Mnemosyne graph+vector DB) use the
+  # same port — they are differentiated by hostname only.
+  - job_name: 'neo4j'
+    static_configs:
+      - targets:
+          - 'ariel.incus:22094'
+          - 'umbriel.incus:22094'
+    metrics_path: '/metrics'
+    scrape_interval: 15s
+
 # Red Panda Approved Prometheus Configuration