[Feature Request] Add `language` parameter to `/v1/tool/search-narrative-candidates`

[BRAYC1330]

Situation

The endpoint /v1/tool/search-narrative-candidates does not support a language query parameter. As a result, keyword searches return mixed-language results (often predominantly Chinese), regardless of the client's locale.

This breaks i18n for bots, dashboards, and apps that expect English-only (or locale-specific) results.

Expected Behavior

Add a language parameter matching the behavior of /v1/tool/list-trending-topics:

- name: language
  in: query
  description: 'Filter results by language/locale. Affects tokenization and trend definition.'
  required: false
  schema:
    type: string
    enum: [zh, en, ko]
    default: en
  example: en

Current Workaround
Clients must post-filter results by detecting Latin characters or using language-detection libraries. This is inefficient and error-prone.
Why This Matters

Enables reliable English-only keyword search for non-CN users
Critical for automated tools (bots, analytics dashboards) that consume this API
Aligns with existing /list-trending-topics?language=en pattern — consistency improves DX

Reference

Endpoint with language support: /v1/tool/list-trending-topics
OpenAPI spec location: chainbase-labs/chainbase-docs/api-reference/tops-api/publicapi.yaml

Impact

Breaking change
Backward compatible (new optional param)
Requires migration

Thanks for maintaining this awesome API!