Support Cloud Serverless InfluxQL through the v1-compatible /query API

[jstirnaman]

Problem

query_influxql is advertised for Cloud Serverless, but QueryService.executeInfluxqlQuery() falls through to an unsupported-product error for that product type.

Cloud Serverless supports InfluxQL through its v1-compatible /query endpoint, rather than /api/v3/query_influxql. The endpoint requires an existing DBRP mapping for the requested database/bucket.

Expected behavior

Route Cloud Serverless query_influxql requests through the documented v1-compatible /query API, preserving the product's Token authentication and surfacing DBRP-mapping failures as structured MCP errors.

Acceptance criteria

• Cloud Serverless query_influxql uses the v1 /query API with database and query parameters.
• Read-only query validation and bounded-result behavior are retained.
• A missing DBRP mapping returns a clear structured error with a remediation hint.
• Product-routing tests cover successful dispatch and the DBRP-mapping failure path.

References

• Use InfluxQL and the v1 HTTP query API
• Cloud Serverless v1 API compatibility and DBRP mappings