docs: state that LibreChat has no desktop installer on the local install hub (#758)

A reader on /de/docs/local reported that they wanted a Windows app. The
Local Installation hub renders three install cards and no prose, so
nothing on the page tells a reader that LibreChat is a self-hosted web
application rather than something you download and run natively.

/docs already carries this clarification (added in #600), but the install
hub is a separate entry point that readers reach directly from search and
from the sidebar, so that note never reaches them. The complaint arriving
again on /docs/local is evidence that one placement is not enough.

Adds a short callout that answers the question directly and points Windows
readers at Docker Desktop. The localhost URL is scoped to Docker and npm,
since the Helm chart deploys to a Kubernetes cluster and is reached through
cluster networking rather than a local address. Also widens the page
description so the expectation is set in search results.

Verified against the app source at origin/dev: LibreChat has no Electron,
Tauri, or other desktop packaging, and PORT defaults to 3080 in
.env.example.

Discord feedback ID: 1546161795104768073


Claude-Session: https://claude.ai/code/session_01UqsVMs6sqXvDj8KvRut897

Co-authored-by: Claude Opus 5 (1M context) <noreply@anthropic.com>

Author: berry-13

content/docs/local/index.mdx

@@ -1,9 +1,15 @@
 ---
 title: Local Installation
 icon: Monitor
-description: How to install LibreChat locally
+description: Install LibreChat yourself with Docker, npm, or a Helm chart. It is a self-hosted web app, not a desktop installer.
 ---
 
+<Callout type="info" title="Is there a Windows or macOS app?">
+
+No. LibreChat is a self-hosted web application, so there is no `.exe`, `.dmg`, or AppImage to download: you install it yourself using one of the methods below, then use it in your browser. Docker and npm run it on your own machine on Windows, macOS, or Linux and serve it at [http://localhost:3080](http://localhost:3080); on Windows, [Docker Desktop](/docs/local/docker) is the simplest starting point. The Helm chart deploys to a Kubernetes cluster instead, and is reached through your cluster's networking.
+
+</Callout>
+
 <LocalInstallHub />
 
 <Callout type="info" title="Looking for a desktop installer?">