docs: add application conventions for health checks, logging, and endpoints

Establish standardized conventions across all Ouranos services:
- Kubernetes-style health endpoints (/live, /ready, /metrics)
- Logging level guidelines (health checks at DEBUG only)
- Protected vs unprotected endpoint definitions
- Prometheus metrics, browser telemetry, and Docker networking standards
- Update daedalus HAProxy health_path from /api/health to /ready/

ansible/inventory/host_vars/titania.incus.yml

@@ -118,7 +118,7 @@ haproxy_backends:
   - subdomain: "daedalus"
     backend_host: "puck.incus"
     backend_port: 20080
-    health_path: "/api/health"
+    health_path: "/ready/"
     timeout_server: 120s
 
   - subdomain: "lobechat"