feat: add MCP healthcheck probes and new templates (grafana, home-assistant, node-red)

- Add healthCheck spec to templates and servers (tool, arguments, interval, timeout, failureThreshold)
- Add healthStatus, lastHealthCheck, events fields to instances
- Create grafana, home-assistant, node-red templates with healthcheck probes
- Add healthcheck probes to existing templates (github, slack, postgres, jira)
- Show HEALTH column in `get instances` and Events section in `describe instance`
- Display healthCheck details in `describe server` and `describe template`
- Schema + storage + display only; actual probe runner is future work

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

templates/jira.yaml

@@ -4,6 +4,11 @@ description: Jira MCP server for issues, projects, and boards
 packageName: "@anthropic/jira-mcp"
 transport: STDIO
 repositoryUrl: https://github.com/modelcontextprotocol/servers/tree/main/src/jira
+healthCheck:
+  tool: search_issues
+  arguments:
+    jql: "created >= -1d"
+    maxResults: 1
 env:
   - name: JIRA_URL
     description: Jira instance URL (e.g. https://company.atlassian.net)