Add Dockerfile and build system for Jupyter image

Created docker/ directory with:
- Dockerfile.jupyter: Extends mcp-forge/python:3.12 with ipykernel 6.29.0
- build-images.sh: Build script with testing
- README.md: Complete documentation and usage instructions

Image Details:
- Base: mcp-forge/python:3.12 (python:3.12-slim)
- Size: 196 MB (~73 MB added for ipykernel + dependencies)
- Includes: ipykernel, jupyter-client, pyzmq, ipython, debugpy, etc.
- Version: 6.29.0 (matches host jupyter-client compatibility)

Build tested and verified:
✓ ipykernel imports correctly (6.29.0)
✓ kernel launcher works
✓ Image ready for use

Next: Update config and run integration tests

docker/README.md

@@ -0,0 +1,107 @@
+# Docker Images for MCP-Forge
+
+This directory contains Dockerfiles for building MCP-Forge container images.
+
+## Images
+
+### Jupyter Image (`mcp-forge/jupyter:latest`)
+
+**Purpose**: Provides Python environment with ipykernel for stateful Jupyter-based execution.
+
+**Base**: `mcp-forge/python:3.12` (which is `python:3.12-slim`)
+
+**Added Components**:
+- `ipykernel` 6.29.0 - Jupyter kernel for Python
+
+**Build Command**:
+```bash
+# From the mcp-forge project root:
+podman build -f docker/Dockerfile.jupyter -t mcp-forge/jupyter:latest .
+```
+
+**Usage**: This image is used automatically by the Jupyter backend when creating stateful sessions. The kernel communicates with the host via ZMQ over host networking.
+
+**Size**: ~130-140 MB (adds ~10-15 MB to base Python image)
+
+## Base Python Images
+
+The base Python images should already exist:
+```bash
+podman tag python:3.11-slim mcp-forge/python:3.11
+podman tag python:3.12-slim mcp-forge/python:3.12
+```
+
+If not, pull and tag them:
+```bash
+podman pull python:3.11-slim
+podman tag python:3.11-slim mcp-forge/python:3.11
+
+podman pull python:3.12-slim  
+podman tag python:3.12-slim mcp-forge/python:3.12
+```
+
+## Building All Images
+
+To build/verify all images at once:
+
+```bash
+#!/bin/bash
+# From project root
+
+# Ensure base images exist
+podman pull python:3.11-slim
+podman pull python:3.12-slim
+podman tag python:3.11-slim mcp-forge/python:3.11
+podman tag python:3.12-slim mcp-forge/python:3.12
+
+# Build Jupyter image
+podman build -f docker/Dockerfile.jupyter -t mcp-forge/jupyter:latest .
+
+# Verify all images
+podman images | grep mcp-forge
+```
+
+## Testing the Jupyter Image
+
+Quick test to verify ipykernel is working:
+
+```bash
+# Test that ipykernel is installed
+podman run --rm mcp-forge/jupyter:latest python -c "import ipykernel; print(ipykernel.__version__)"
+
+# Test kernel launcher exists
+podman run --rm mcp-forge/jupyter:latest python -m ipykernel_launcher --help
+```
+
+Expected output:
+```
+6.29.0
+usage: ipykernel_launcher [-h] [-f FILE] ...
+```
+
+## Image Sizes
+
+Expected sizes:
+- `mcp-forge/python:3.11` - ~129 MB
+- `mcp-forge/python:3.12` - ~123 MB
+- `mcp-forge/jupyter:latest` - ~135-140 MB
+
+## Updating Images
+
+To update the Jupyter image with a newer ipykernel version:
+
+1. Edit `docker/Dockerfile.jupyter`
+2. Update the ipykernel version number
+3. Rebuild: `podman build -f docker/Dockerfile.jupyter -t mcp-forge/jupyter:latest .`
+4. Test with integration tests
+5. Tag with version: `podman tag mcp-forge/jupyter:latest mcp-forge/jupyter:v1.0.1`
+
+## Security Notes
+
+All images run with:
+- `network_mode: host` (for Jupyter kernels only, to enable ZMQ communication)
+- `read_only: True` (filesystem is read-only except mounted volumes)
+- `security_opt: ["no-new-privileges"]`
+- Non-root user (UID:GID 1000:1000)
+
+The host networking is required for ZMQ port communication between the host-side `jupyter-client` and the container-side `ipykernel`.