docs: add Rust and Node.js prerequisites to build instructions

- Add installation instructions for Rust via rustup.sh
- Include rustup target add x86_64-apple-darwin for universal binary support
- Note Node.js requirement for web frontend build

README.md

@@ -141,6 +141,17 @@ For technical details, see [ARCHITECTURE.md](docs/ARCHITECTURE.md).
 
 ## Building from Source
 
+### Prerequisites
+
+- **Rust**: Install via [https://rustup.sh/](https://rustup.sh/)
+  ```bash
+  # After installing Rust, add the x86_64 target for universal binary support
+  rustup target add x86_64-apple-darwin
+  ```
+- **Node.js**: Required for building the web frontend
+
+### Build Steps
+
 ```bash
 # Clone the repository
 git clone https://github.com/amantus-ai/vibetunnel.git