feat: add /api/v1/language endpoint for Go/Python runtime detection (#16952)

Both backends serve GET /api/v1/language. Frontend calls it once and
caches. By this way, front end can know the backend is go or python and
thus can determine which part of logic to load.

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Co-authored-by: Claude <noreply@anthropic.com>

web/src/utils/api.ts

@@ -181,6 +181,7 @@ export default {
     `${restAPIv1}/datasets/${datasetId}/ingestions/${logId}`,
   fetchPipelineDatasetLogs: (datasetId: string) =>
     `${restAPIv1}/datasets/${datasetId}/ingestions`,
+  listPipelines: `${restAPIv1}/pipelines?type=builtin`,
   runIndex: (datasetId: string, indexType: string) =>
     `${restAPIv1}/datasets/${datasetId}/index?type=${indexType.toLowerCase()}`,
   traceIndex: (datasetId: string, indexType: string) =>