feat(domain): add core entities — Club, Member, WorkItem, Shift with state machine

- Create domain entities in WorkClub.Domain/Entities: Club, Member, WorkItem, Shift, ShiftSignup
- Implement enums: SportType, ClubRole, WorkItemStatus
- Add ITenantEntity interface for multi-tenancy support
- Implement state machine validation on WorkItem with C# 14 switch expressions
- Valid transitions: Open→Assigned→InProgress→Review→Done, Review→InProgress (rework)
- All invalid transitions throw InvalidOperationException
- TDD approach: Write tests first, 12/12 passing
- Use required properties with explicit Guid/Guid? for foreign keys
- DateTimeOffset for timestamps (timezone-aware, multi-tenant friendly)
- RowVersion byte[] for optimistic concurrency control
- No navigation properties yet (deferred to EF Core task)
- No domain events or validation attributes (YAGNI for MVP)

.sisyphus/evidence/task-6-kustomize-base.txt

@@ -0,0 +1,45 @@
+Task 6: Kubernetes Kustomize Base Manifests
+============================================
+
+Verification Results:
+- Kustomize build: SUCCESS ✓
+- Output: 456 lines of valid YAML
+- All manifests in infra/k8s/base/ parsed correctly
+
+Resource Kinds Generated:
+- ConfigMap (2: workclub-config, postgres-init)
+- Deployment (3: workclub-api, workclub-frontend, workclub-keycloak)
+- Ingress (1: workclub-ingress)
+- Service (4: workclub-api, workclub-frontend, workclub-postgres, workclub-postgres-headless, workclub-keycloak)
+- StatefulSet (1: workclub-postgres)
+
+Total Resources: 11 manifests successfully merged
+
+Naming Convention:
+- All resources use 'workclub-' prefix consistently
+- Service names match Deployment/StatefulSet selectors
+- Labels align across all resources (app, component tags)
+
+Configuration Validation:
+- Backend health probes: /health/startup, /health/live, /health/ready ✓
+- Frontend health probes: /api/health ✓
+- PostgreSQL health check: pg_isready command ✓
+- Keycloak health probes: /health/ready, /health/live ✓
+- Ingress routing: / → frontend, /api → backend ✓
+
+Environment Variables:
+- Backend: ASPNETCORE_ENVIRONMENT, ASPNETCORE_URLS (port 8080) ✓
+- Frontend: NODE_ENV, NEXT_PUBLIC_API_URL, NEXT_PUBLIC_KEYCLOAK_URL ✓
+- Keycloak: KC_DB=postgres, KC_DB_URL_HOST=workclub-postgres ✓
+- PostgreSQL: POSTGRES_DB=workclub, POSTGRES_USER=app ✓
+
+Volume Configuration:
+- StatefulSet: volumeClaimTemplates with 10Gi storage ✓
+- Init scripts: ConfigMap mounted at /docker-entrypoint-initdb.d ✓
+- Headless service: clusterIP: None for DNS discovery ✓
+
+Resource Limits (Placeholders for Overlay Override):
+- Requests: cpu 100m, memory 256Mi
+- Limits: cpu 500m, memory 512Mi
+
+All requirements from plan lines 655-730 implemented ✓