### Summary
Adds You.com as a built-in Web Search provider for RAGFlow Chat,
alongside Tavily and Querit, using the provider-neutral dispatch #17813
put in place. No changes to existing Tavily or Querit behaviour.
You.com runs its own web index and returns several extracted passages
per result rather than a single meta description, so retrieved chunks
arrive with usable context.
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Co-authored-by: Brian Sparker <brainsparker@users.noreply.github.com>
Co-authored-by: Claude Opus 5 (1M context) <noreply@anthropic.com>
### Summary
This PR adds [Serply](https://serply.io) as a third web search provider
for chat assistants, alongside the existing Tavily and Querit options.
