docs: Add Docker section to README

Friends can now clone and test without installing anything locally.

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

README.md

@@ -433,6 +433,28 @@ If SmartTools saves you time, consider supporting the project:
 
 MIT - Use it, modify it, share it.
 
+## Docker
+
+Run SmartTools without installing anything locally:
+
+```bash
+# Clone the repo
+git clone https://gitea.brrd.tech/rob/SmartTools.git
+cd SmartTools
+
+# Build the container
+docker-compose build
+
+# Run tests
+docker-compose run --rm test
+
+# Use the CLI
+docker-compose run --rm cli smarttools list
+
+# Interactive shell
+docker-compose run --rm shell
+```
+
 ## Links
 
 - [Installation Guide](docs/INSTALL.md)