Add devcontainer configuration for development

This adds a complete development container configuration that includes:
- Bun (for formatting and scripts)
- Terraform (for module development)
- Docker-in-Docker (for running tests)
- VS Code extensions and settings

The devcontainer automatically installs all dependencies on creation,
making it easy for contributors to start developing without manual setup.

Resolves #51

Author: ktamas77

.devcontainer/README.md

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+# Development Container
+
+This directory contains a Dev Container configuration that provides a complete development environment for the Coder Registry with all required dependencies pre-installed.
+
+## What's Included
+
+The dev container includes:
+
+- **Bun** - JavaScript runtime and package manager (for formatting and scripts)
+- **Terraform** - Infrastructure as code tool (for module development)
+- **Docker** - Container runtime (for running tests with `--network=host`)
+- **Git** - Version control
+- **VS Code Extensions**:
+  - HashiCorp Terraform
+  - Bun for VS Code
+  - Prettier
+
+## Quick Start
+
+### Using VS Code
+
+1. Install the [Dev Containers extension](https://marketplace.visualstudio.com/items?itemName=ms-vscode-remote.remote-containers)
+2. Open this repository in VS Code
+3. When prompted, click "Reopen in Container" (or run the command "Dev Containers: Reopen in Container")
+4. Wait for the container to build and dependencies to install
+5. Start developing!
+
+### Using GitHub Codespaces
+
+1. Click the "Code" button on the GitHub repository
+2. Select "Codespaces" tab
+3. Click "Create codespace on main"
+4. Wait for the environment to be ready
+5. Start developing!
+
+### Using Coder
+
+You can also use this with Coder's `docker-devcontainer` template:
+
+1. Create a new workspace using the `docker-devcontainer` template
+2. Point it to this repository
+3. Coder will automatically use the `.devcontainer/devcontainer.json` configuration
+
+## What Happens on Startup
+
+When the container is created, it automatically:
+
+1. Installs Bun via the official installation script
+2. Runs `bun install` to install all project dependencies
+3. Sets up PATH to include Bun binaries
+4. Mounts Docker socket for Docker-in-Docker support
+5. Configures VS Code with recommended extensions and settings
+
+## Development Workflow
+
+Once inside the container, you can use all the standard commands:
+
+```bash
+# Format code
+bun run fmt
+
+# Run tests
+bun run test
+
+# Create a new module
+./scripts/new_module.sh namespace/module-name
+
+# Test a specific module
+cd registry/namespace/modules/module-name
+terraform init -upgrade
+terraform test -verbose
+```
+
+## Notes
+
+- The container uses `--network=host` flag which is required for Terraform tests
+- Docker socket is mounted to support Docker-based tests
+- All dependencies are installed automatically on container creation
+- The environment is based on Ubuntu for maximum compatibility
+
+## Troubleshooting
+
+**Bun not found after container creation:**
+- Restart the terminal or run: `source ~/.bashrc`
+- The PATH should include `~/.bun/bin`
+
+**Docker not working:**
+- Ensure Docker is running on your host machine
+- Check that Docker socket is properly mounted
+
+**Tests failing:**
+- Make sure you're using Linux or a compatible Docker runtime (Colima/OrbStack on macOS)
+- Verify Docker has network access with `--network=host`
+
+## Contributing
+
+This dev container configuration is part of the Coder Registry repository. If you find issues or have suggestions for improvements, please open an issue or pull request!

.devcontainer/devcontainer.json

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+{
+  "name": "Coder Registry Development",
+  "image": "mcr.microsoft.com/devcontainers/base:ubuntu",
+
+  "features": {
+    "ghcr.io/devcontainers/features/docker-in-docker:2": {},
+    "ghcr.io/devcontainers/features/terraform:1": {
+      "version": "latest"
+    },
+    "ghcr.io/devcontainers/features/git:1": {},
+    "ghcr.io/devcontainers/features/common-utils:2": {
+      "installZsh": true,
+      "installOhMyZsh": true
+    }
+  },
+
+  "postCreateCommand": "curl -fsSL https://bun.sh/install | bash && export BUN_INSTALL=\"$HOME/.bun\" && export PATH=\"$BUN_INSTALL/bin:$PATH\" && bun install",
+
+  "customizations": {
+    "vscode": {
+      "extensions": [
+        "hashicorp.terraform",
+        "oven.bun-vscode",
+        "esbenp.prettier-vscode"
+      ],
+      "settings": {
+        "files.exclude": {
+          "**/terraform.tfstate": true,
+          "**/.terraform": true
+        },
+        "editor.formatOnSave": true,
+        "editor.defaultFormatter": "esbenp.prettier-vscode",
+        "[terraform]": {
+          "editor.defaultFormatter": "hashicorp.terraform"
+        }
+      }
+    }
+  },
+
+  "remoteEnv": {
+    "BUN_INSTALL": "${containerHome}/.bun",
+    "PATH": "${containerHome}/.bun/bin:${containerEnv:PATH}"
+  },
+
+  "forwardPorts": [],
+
+  "mounts": [
+    "source=/var/run/docker.sock,target=/var/run/docker.sock,type=bind"
+  ],
+
+  "runArgs": ["--network=host"]
+}