Archive observability change, sync specs to main

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

openspec/specs/infrastructure/spec.md

@@ -121,3 +121,17 @@ Grafana SHALL authenticate users via GitHub OAuth, restricted to the trails-cool
 #### Scenario: No password-based login
 - **WHEN** Grafana is deployed
 - **THEN** the login form is disabled and only GitHub OAuth is available
+
+### Requirement: Docker Compose deployment
+All services SHALL be deployed via Docker Compose, including Grafana, Prometheus, and Loki for the flagship instance.
+
+#### Scenario: Monitoring stack starts
+- **WHEN** `docker compose up -d` is run
+- **THEN** Grafana, Prometheus, and Loki containers start alongside the application containers
+
+### Requirement: Caddy access logging
+Caddy SHALL emit structured JSON access logs for all requests.
+
+#### Scenario: Access log emitted
+- **WHEN** any HTTP request passes through Caddy
+- **THEN** a JSON log line with remote IP, method, path, status, and duration is written to stdout