docs: update Docker documentation to reflect simplified setup

- Removed multi-stage Dockerfile complexity
- Updated documentation to match single Dockerfile approach
- Both dev and prod modes use 'yarn snapp start'
- Development uses volume mounts for hot reload
- Production uses built-in code without volumes
- Simplified and cleaner Docker setup

Author: VargaJoe

DOCKER.md

@@ -0,0 +1,129 @@
+# Docker Setup for SenseNet Client
+
+This guide explains how to run the SenseNet client application using Docker.
+
+## 🚀 Quick Start
+
+### Development (with hot reload)
+```bash
+docker-compose -f docker-compose.dev.yml up -d
+```
+- **URL**: http://localhost:8080
+- **Hot reload**: ✅ File changes are instantly reflected
+- **Use case**: Active development
+
+### Production
+```bash
+docker-compose -f docker-compose.prod.yml up -d
+```
+- **URL**: http://localhost:8080
+- **Hot reload**: ❌ Static built files
+- **Use case**: Testing production builds, deployment
+
+## 📁 Files Overview
+
+| File | Purpose |
+|------|---------|
+| `Dockerfile` | Single Docker image for both dev and prod |
+| `docker-compose.dev.yml` | Development setup with volume mounts |
+| `docker-compose.prod.yml` | Production setup without volume mounts |
+| `.dockerignore` | Excludes unnecessary files from build context |
+
+## 🔧 How It Works
+
+### Development Mode
+- **Volume mounting**: Your local code is mounted into the container
+- **File watching**: Changes trigger automatic rebuilds
+- **Command**: `yarn snapp start` (webpack dev server with hot reload)
+
+### Production Mode
+- **Built files**: Uses pre-built static files inside the container  
+- **No volumes**: Container is self-contained
+- **Command**: `yarn snapp start` (same command, but runs webpack dev server on built files)
+
+## 🛠️ Common Commands
+
+```bash
+# Start development
+docker-compose -f docker-compose.dev.yml up -d
+
+# Stop development
+docker-compose -f docker-compose.dev.yml down
+
+# Rebuild and start (after dependency changes)
+docker-compose -f docker-compose.dev.yml up --build -d
+
+# View logs
+docker-compose -f docker-compose.dev.yml logs -f
+
+# Start production
+docker-compose -f docker-compose.prod.yml up -d
+```
+
+## 🐳 Docker Images
+
+Automatic builds are available on DockerHub:
+
+```bash
+# Latest development build
+docker pull sensenetcsp/sn-client:feature-docker-containerization
+
+# Specific commit
+docker pull sensenetcsp/sn-client:feature-docker-containerization-abc1234
+
+# Production (when merged to main)
+docker pull sensenetcsp/sn-client:latest
+```
+
+## ⚙️ Configuration
+
+### Environment Variables
+Both compose files support these environment variables:
+
+- `NODE_ENV`: `development` or `production`
+- `AUTH_TYPE`: `SNAuth` or `IdentityServer`
+- `CHOKIDAR_USEPOLLING`: `true` (dev only, for file watching)
+- `WATCHPACK_POLLING`: `true` (dev only, for webpack)
+
+### Port Configuration
+- **Default**: Port 8080 for both dev and prod
+- **Customizable**: Change the host port in docker-compose files
+
+## 🔍 Troubleshooting
+
+### Container won't start
+```bash
+# Check logs
+docker-compose -f docker-compose.dev.yml logs
+
+# Rebuild from scratch
+docker-compose -f docker-compose.dev.yml down
+docker-compose -f docker-compose.dev.yml up --build
+```
+
+### Hot reload not working
+- Ensure you're using the dev compose file
+- Restart the container if file watching stops working
+
+### Port already in use
+```bash
+# Change the port in docker-compose file
+ports:
+  - "3000:8080"  # Use port 3000 instead of 8080
+```
+
+## 📦 Build Process
+
+The Docker build process:
+1. **Copy source code** (excluding files in `.dockerignore`)
+2. **Install dependencies** with `yarn install`
+3. **Build packages** with `yarn build`
+4. **Start application** with `yarn snapp start`
+
+## 🚀 CI/CD
+
+GitHub Actions automatically builds and pushes Docker images when:
+- Code is pushed to `feature/docker-containerization`
+- Pull requests target `develop`, `main`, or `feature/sn-auth-package-extraimprovements`
+
+Images are tagged based on branch names and commit SHAs for easy identification.