docs: web search needs a compose example and a self-hosted stack path

[berry-13]

Three submissions ask for web search documentation that covers deploying the whole stack, and for a fully self-hosted option.

Reports (verbatim, sanitized)

Page	Report
.../object_structure/web_search	"add docker compose configuration example to deploy the whole system with docker compose up"
/docs/features/web_search	"Add (link to or direct) docker configuration documentation to add web search services to the deployment"
.../object_structure/web_search	"This setup does not allow for fully locally hosted web search setup. to support fully locally hosted web search you would need to support tools like crawl4ai and a locally hosted reranker. please add documentation to set that up"

Current state

web_search.mdx was substantially improved by #732, which added searxngSearchOptions, the SSRF/allowedAddresses section, and engine guidance. Two gaps remain:

1. No compose example. The SearXNG setup guide is a Docker Desktop click-through. There is no docker-compose.override.yml fragment that brings up SearXNG alongside LibreChat, even though allowedAddresses and the service-name URL are exactly the parts people get wrong.
2. No fully self-hosted path. Per webSearchSchema in packages/data-provider/src/config.ts, the scraper providers are Firecrawl / Serper / Tavily and the rerankers are Jina / Cohere. Firecrawl and Jina can be self-hosted or given a custom URL (firecrawlApiUrl, jinaApiUrl), but that combination is undocumented, and there is no crawl4ai integration at all.

Item 2 is partly an upstream capability question (does LibreChat want a crawl4ai scraper?) and partly a docs question (can a Firecrawl + Jina self-hosted combination be documented today?). The docs half is actionable now; the crawl4ai request belongs upstream if it is wanted.

Discord feedback IDs: 1526235582680793151, 1526235208259735644, 1526251900801126614.