Add generateFlowchart contract to goto-anything contracts and update
use-workflow-vibe.tsx to use the new typed oRPC service function.
This completes the oRPC migration for the entire goto-anything feature
including vibe workflow functionality.
Replace direct service calls with typed oRPC contracts for apps, datasets,
and plugins search in the goto-anything feature. This provides better type
safety and consistent API patterns across the codebase.
yyh