Enhance README.md with detailed architecture diagram and update AI provider information

Author: davidfowl

README.md

@@ -2,38 +2,105 @@
 
 Aspire AI Chat is a full-stack chat sample that combines modern technologies to deliver a ChatGPT-like experience.
 
+## Architecture
+
+```mermaid
+graph TB
+    User[User Browser]
+    
+    subgraph "YARP Reverse Proxy"
+        YARP[chatui - YARP]
+    end
+    
+    subgraph "Frontend"
+        UI[React + TypeScript UI<br/>Vite Build]
+    end
+    
+    subgraph "Backend API"
+        API[ChatApi - ASP.NET Core<br/>SignalR Hub]
+    end
+    
+    subgraph "Data Layer"
+        PG[(PostgreSQL<br/>Conversation History)]
+        Redis[(Redis<br/>Message Stream Cache)]
+    end
+    
+    subgraph "AI Layer"
+        LLM{AI Provider}
+        Ollama[Ollama<br/>phi4 model<br/>Linux/Windows]
+        OpenAI[OpenAI<br/>gpt-4.1<br/>macOS/Production]
+    end
+    
+    User -->|HTTP/WS| YARP
+    YARP -->|Static Files| UI
+    YARP -->|/api/*| API
+    
+    API -->|SignalR| User
+    API -->|EF Core| PG
+    API -->|Pub/Sub| Redis
+    API -->|IChatClient| LLM
+    
+    LLM -.->|Local| Ollama
+    LLM -.->|Cloud| OpenAI
+    
+    style YARP fill:#e1f5ff
+    style API fill:#fff3e0
+    style UI fill:#f3e5f5
+    style PG fill:#e8f5e9
+    style Redis fill:#ffebee
+    style LLM fill:#fff9c4
+```
+
 ## High-Level Overview
 
 - **Backend API:**  
-  The backend is built with **ASP.NET Core** and interacts with an LLM using **Microsoft.Extensions.AI**. It leverages `IChatClient` to abstract the interaction between the API and the model. Chat responses are streamed back to the client using stream JSON array responses.
+  The backend is built with **ASP.NET Core** and interacts with an LLM using **Microsoft.Extensions.AI**. It leverages `IChatClient` to abstract the interaction between the API and the model. Chat responses are streamed back to the client using **SignalR** for real-time communication.
 
 - **Data & Persistence:**  
-  Uses **Entity Framework Core** with **PostgreSQL** for reliable relational data storage. The project includes database migrations for easy setup and version control of the schema.
+  Uses **Entity Framework Core** with **PostgreSQL** for reliable relational data storage. **Redis** is used for caching and broadcasting live message streams across multiple clients.
 
 - **AI & Chat Capabilities:**  
-  - Uses **Ollama** (via OllamaSharp) for local inference, enabling context-aware responses.  
-  - In production, the application switches to [**OpenAI**](https://openai.com/) for LLM capabilities.
+  - Uses **Ollama** (via OllamaSharp) for local inference on Linux/Windows.  
+  - On macOS, the application uses [**OpenAI**](https://openai.com/) directly for better compatibility.
+  - In production, the application can be configured to use various AI providers through the abstraction layer.
 
 - **Frontend UI:**  
-  Built with **React**, the user interface offers a modern and interactive chat experience. The React application is built and hosted using [**Caddy**](https://caddyserver.com/).
+  Built with **React** and **TypeScript** using **Vite** for fast development and builds. The UI provides a modern chat interface with support for markdown rendering and conversation history.
+
+- **Reverse Proxy & Serving:**  
+  Uses **YARP** (Yet Another Reverse Proxy) to serve the static frontend and proxy API requests, providing a unified endpoint.
 
 ## Getting Started
 
 ### Prerequisites
 
-- [.NET 9.0](https://dotnet.microsoft.com/en-us/download/dotnet/9.0)
+- [.NET 10.0 SDK](https://dotnet.microsoft.com/en-us/download/dotnet/10.0)
 - [Docker](https://www.docker.com/get-started) or [Podman](https://podman-desktop.io/)
 - [Node.js](https://nodejs.org/) (LTS version recommended)
 
 ### Running the Application
 
-Run the [AIChat.AppHost](AIChat.AppHost) project. This project uses  
-[.NET Aspire](https://learn.microsoft.com/en-us/dotnet/aspire/get-started/aspire-overview)  
-to run the application in a container.
+Run the [AIChat.AppHost](AIChat.AppHost) project using the .NET Aspire tooling:
+
+```bash
+aspire run
+```
+
+This project uses [.NET Aspire](https://learn.microsoft.com/en-us/dotnet/aspire/get-started/aspire-overview) to orchestrate the application components in containers.
 
 ### Configuration
 
-- By default, the application uses **Ollama** for local inference.  
-- To use **OpenAI**, set the appropriate configuration values (e.g., API keys, endpoints).  
-- The PostgreSQL database will be automatically created and migrated when running with Aspire.
+- By default, the application uses **Ollama** (phi4 model) for local inference on Linux/Windows.  
+- On **macOS**, it automatically switches to **OpenAI** and will prompt for your OpenAI API key if not already configured.
+- The **PostgreSQL** database and **Redis** cache are automatically provisioned when running with Aspire.
+- Access the Aspire dashboard to monitor resources and view logs.
+
+## CI/CD
+
+The project includes a GitHub Actions workflow that:
+
+- Builds container images for both the API and UI
+- Tags images with format: `<branch>-<build-number>-<git-sha>`
+- Pushes images to GitHub Container Registry (GHCR)
 
+Images are available at: `ghcr.io/<owner>/chatapi` and `ghcr.io/<owner>/chatui`