feat: Add tool server health status endpoint

[IVVI0927]

Summary

I am considering adding an admin-only endpoint that reports the health status of all configured tool servers in one request.

Proposed endpoint:

GET /api/v1/configs/tool_servers/status

The endpoint would read the existing TOOL_SERVER_CONNECTIONS config and return a status summary for each configured MCP or OpenAPI tool server.

Motivation

Currently, POST /api/v1/configs/tool_servers/verify can verify one tool server at a time, but it requires the client to provide the full connection config in the request body.

That works well during setup, but it is less convenient for:

• admin dashboards
• debugging unavailable tools
• automated health checks
• seeing which configured server is failing without checking each one manually

Proposed response shape

{
  "servers": [
    {
      "id": "server-id",
      "name": "Server Name",
      "url": "http://localhost:8080",
      "type": "mcp",
      "status": "ok",
      "latency_ms": 42.1,
      "tools_count": 5,
      "error": null
    }
  ]
}

Possible status values:

• ok: server responded successfully
• error: server was unreachable or returned an invalid response
• skipped: server cannot be checked by this endpoint, for example OAuth-protected MCP servers that require a live user session

Design notes

• Admin-only endpoint
• Read-only behavior
• No database changes
• No new dependencies
• Probe configured servers concurrently
• Use a short timeout so one unhealthy server does not block the whole response
• Reuse existing MCP/OpenAPI tool server logic where possible