Add uv for dependency management and update workshop materials

README.md

@@ -37,15 +37,24 @@ Each section has its own `README.md` with a full walkthrough, exercises, and any
 
 ### Python environment
 
-Create a virtual environment once and reuse it across sections:
+Install [uv](https://docs.astral.sh/uv/getting-started/installation/) (a fast Python package manager), then:
 
 ```bash
-python3 -m venv llm-workshop
-source llm-workshop/bin/activate
-pip install numpy torch matplotlib
+uv sync
 ```
 
-Sections 03 and 04 have additional dependencies listed in their `requirements.txt` files.
+This creates a `.venv/` virtual environment and installs all dependencies from the lock file. To run scripts:
+
+```bash
+uv run python 05-neural-networks/nn_torch.py
+```
+
+Or activate the environment directly:
+
+```bash
+source .venv/bin/activate
+python 05-neural-networks/nn_torch.py
+```
 
 ## License