Initial commit: Add universal Just recipes

- container.just: Universal container operations (start, stop, logs, shell, exec, status)
- registry.just: GitHub Container Registry authentication
- images.just: Universal image build/push/pull operations
- README.md: Documentation and usage instructions

These recipes work universally across any project with containerfiles.

README.md

@@ -0,0 +1,49 @@
+# Just Commons
+
+Universal Just command recipes for container management across projects.
+
+## Overview
+
+This repository contains reusable Just recipes for:
+- **Container operations**: start, stop, restart, logs, shell, exec, status
+- **Registry authentication**: login, logout, status checks for GitHub Container Registry
+- **Image operations**: build, push, pull, tag, test, info, clean
+
+## Usage
+
+Add as a Git submodule to your project:
+
+```bash
+git submodule add git@github.com:shadoll/just-commons.git
+```
+
+Import in your `justfile`:
+
+```bash
+# Import universal commands
+import 'just-commons/container.just'
+import 'just-commons/registry.just'
+import 'just-commons/images.just'
+
+# Your project-specific commands
+import 'just/postgres.just'
+import 'just/servapp.just'
+```
+
+## Files
+
+- `container.just` - Universal container operations (start, stop, logs, shell, exec, status)
+- `registry.just` - GitHub Container Registry authentication
+- `images.just` - Universal image build/push/pull operations
+
+## Requirements
+
+- Just command runner
+- Docker or Podman
+- Git
+
+## Projects Using This
+
+- [servass](https://github.com/shadoll/servass) - Universal container image management
+- [servass_sh](https://github.com/shadoll/servass_sh) - Production deployment (SH)
+- [servass_ri](https://github.com/shadoll/servass_ri) - Production deployment (RI)