Add Podman support

Adds Podman as an alternative to Docker for developers who cannot easily
use Docker. Podman is a daemonless container engine with Docker-compatible
CLI and compose functionality.

Key features:
- Two-container architecture: development shell and dedicated test container
- Automated setup script with init, test, shell, status, logs, clean commands
- Full test suite compatibility with proper network configuration
- Rootless mode by default
- Comprehensive documentation with troubleshooting guide
- CI parity: tests run identically locally and in GitHub Actions
The test container uses hostname 'http-server' for network tests,
ensuring all HTTP/network tests pass correctly.

Author: that-jill

.gitignore

@@ -16,3 +16,11 @@
 /tmp
 nohup.out
 vendor/
+
+# Podman-specific
+.podman-machine-*
+podman-compose.override.yml
+.env.podman
+
+# VS Code + Podman local settings
+.vscode/settings.local.json

README.md

@@ -954,6 +954,24 @@ $ git clone https://github.com/Shopify/semian.git
 $ cd semian
 ```
 
+## Alternative: Using Podman
+
+If you prefer Podman over Docker, see our [Podman setup guide](docs/PODMAN.md).
+
+Quick start with Podman:
+```bash
+# Initialize everything
+./scripts/podman-setup.sh init
+
+# Run tests
+./scripts/podman-setup.sh test
+
+# Get a development shell
+./scripts/podman-setup.sh shell
+```
+
+The Podman setup provides the same functionality as the Docker setup with full backward compatibility.
+
 ## Visual Studio Code
 
 - Open semian in vscode