Fix empty Caddy and pg_stat_statements panels in service-health dashboard

- Caddy Response Status Codes: caddy_http_responses_total doesn't exist,
  use caddy_http_response_duration_seconds_count which has the code label
- pg_stat_statements: enable extension in init script, add custom queries
  config for postgres-exporter, remove invalid datname filter from query
- Add postgres/queries.yml to cd-infra SCP sources

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

infrastructure/docker-compose.yml

@@ -99,6 +99,9 @@ services:
     restart: unless-stopped
     environment:
       DATA_SOURCE_NAME: postgresql://trails:${POSTGRES_PASSWORD:-trails}@postgres:5432/trails?sslmode=disable
+      PG_EXPORTER_EXTEND_QUERY_PATH: /etc/postgres-exporter/queries.yml
+    volumes:
+      - ./postgres/queries.yml:/etc/postgres-exporter/queries.yml:ro
     depends_on:
       postgres:
         condition: service_healthy