chore(ui): add npm package and dockerfile (#4100)

# What does this PR do?
- sets up package.json for npm `llama-stack-ui` package (will update
llama-stack-ops)
- adds dockerfile for UI docker image

## Test Plan
npx:
npm build && npm pack
LLAMA_STACK_UI_PORT=8322 npx
/Users/erichuang/projects/ui/src/llama_stack_ui/llama-stack-ui-0.4.0-alpha.2.tgz

docker:
cd src/llama_stack_ui
docker build . -f Dockerfile  --tag test_ui --no-cache

❯ docker run -p 8322:8322 \
      -e LLAMA_STACK_UI_PORT=8322 \
      test_ui:latest

docs/docs/distributions/llama_stack_ui.mdx

@@ -0,0 +1,109 @@
+---
+title: Llama Stack UI
+description: Web-based user interface for interacting with Llama Stack servers
+sidebar_label: Llama Stack UI
+sidebar_position: 8
+---
+
+# Llama Stack UI
+
+The Llama Stack UI is a web-based interface for interacting with Llama Stack servers. Built with Next.js and React, it provides a visual way to work with agents, manage resources, and view logs.
+
+## Features
+
+- **Logs & Monitoring**: View chat completions, agent responses, and vector store activity
+- **Vector Stores**: Create and manage vector databases for RAG (Retrieval-Augmented Generation) workflows
+- **Prompt Management**: Create and manage reusable prompts
+
+## Prerequisites
+
+You need a running Llama Stack server. The UI is a client that connects to the Llama Stack backend.
+
+If you don't have a Llama Stack server running yet, see the [Starting Llama Stack Server](../getting_started/starting_llama_stack_server.mdx) guide.
+
+## Running the UI
+
+### Option 1: Using npx (Recommended for Quick Start)
+
+The fastest way to get started is using `npx`:
+
+```bash
+npx llama-stack-ui
+```
+
+This will start the UI server on `http://localhost:8322` (default port).
+
+### Option 2: Using Docker
+
+Run the UI in a container:
+
+```bash
+docker run -p 8322:8322 llamastack/ui
+```
+
+Access the UI at `http://localhost:8322`.
+
+## Environment Variables
+
+The UI can be configured using the following environment variables:
+
+| Variable | Description | Default |
+|----------|-------------|---------|
+| `LLAMA_STACK_BACKEND_URL` | URL of your Llama Stack server | `http://localhost:8321` |
+| `LLAMA_STACK_UI_PORT` | Port for the UI server | `8322` |
+
+If the Llama Stack server is running with authentication enabled, you can configure the UI to use it by setting the following environment variables:
+
+| Variable | Description | Default |
+|----------|-------------|---------|
+| `NEXTAUTH_URL` | NextAuth URL for authentication | `http://localhost:8322` |
+| `GITHUB_CLIENT_ID` | GitHub OAuth client ID (optional, for authentication) | - |
+| `GITHUB_CLIENT_SECRET` | GitHub OAuth client secret (optional, for authentication) | - |
+
+### Setting Environment Variables
+
+#### For npx:
+
+```bash
+LLAMA_STACK_BACKEND_URL=http://localhost:8321 \
+LLAMA_STACK_UI_PORT=8080 \
+npx llama-stack-ui
+```
+
+#### For Docker:
+
+```bash
+docker run -p 8080:8080 \
+  -e LLAMA_STACK_BACKEND_URL=http://localhost:8321 \
+  -e LLAMA_STACK_UI_PORT=8080 \
+  llamastack/ui
+```
+
+## Using the UI
+
+### Managing Resources
+
+- **Vector Stores**: Create vector databases for RAG workflows, view stored documents and embeddings
+- **Prompts**: Create and manage reusable prompt templates
+- **Chat Completions**: View history of chat interactions
+- **Responses**: Browse detailed agent responses and tool calls
+
+## Development
+
+If you want to run the UI from source for development:
+
+```bash
+# From the project root
+cd src/llama_stack_ui
+
+# Install dependencies
+npm install
+
+# Set environment variables
+export LLAMA_STACK_BACKEND_URL=http://localhost:8321
+
+# Start the development server
+npm run dev
+```
+
+The development server will start on `http://localhost:8322` with hot reloading enabled.