fix(test): correct ha-failover test — wrong URL, wrong pod label, missing kubectl

Three bugs:
- GITEA_URL defaulted to localhost:3000; Gitea NodePort is 32166
- Pod label app.kubernetes.io/name=postgresql-ha matched pgpool pod too;
  added component=postgresql to target only postgres nodes
- Used bare 'kubectl' which is not on PATH; switched to 'k3s kubectl'

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

Makefile

@@ -20,4 +20,4 @@ help: ## Show this help
 	  /^[a-zA-Z_-]+:.*?##/ { printf "  \033[36m%-20s\033[0m %s\n", $$1, $$2 } \
 	  /^##@/ { printf "\n\033[1m%s\033[0m\n", substr($$0, 5) }' $(MAKEFILE_LIST)
 
-.PHONY: k3s-install smoke help
+.PHONY: k3s-install smoke test-ha-failover help