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/build-images.sh

@@ -0,0 +1,86 @@
+#!/bin/bash
+# Build MCP-Forge container images
+#
+# Usage: ./build-images.sh [--all|--jupyter]
+
+set -e
+
+SCRIPT_DIR="$(cd "$(dirname "${BASH_SOURCE[0]}")" && pwd)"
+PROJECT_ROOT="$(cd "$SCRIPT_DIR/.." && pwd)"
+
+cd "$PROJECT_ROOT"
+
+build_jupyter() {
+    echo "Building mcp-forge/jupyter:latest..."
+    podman build -f docker/Dockerfile.jupyter -t mcp-forge/jupyter:latest .
+    echo "✓ Built mcp-forge/jupyter:latest"
+}
+
+ensure_base_images() {
+    echo "Ensuring base Python images exist..."
+    
+    # Check if images exist
+    if ! podman image exists mcp-forge/python:3.11; then
+        echo "  Pulling and tagging python:3.11-slim..."
+        podman pull python:3.11-slim
+        podman tag python:3.11-slim mcp-forge/python:3.11
+        echo "  ✓ Created mcp-forge/python:3.11"
+    else
+        echo "  ✓ mcp-forge/python:3.11 exists"
+    fi
+    
+    if ! podman image exists mcp-forge/python:3.12; then
+        echo "  Pulling and tagging python:3.12-slim..."
+        podman pull python:3.12-slim
+        podman tag python:3.12-slim mcp-forge/python:3.12
+        echo "  ✓ Created mcp-forge/python:3.12"
+    else
+        echo "  ✓ mcp-forge/python:3.12 exists"
+    fi
+}
+
+verify_images() {
+    echo ""
+    echo "Verifying images..."
+    echo ""
+    podman images | grep -E "REPOSITORY|mcp-forge"
+}
+
+test_jupyter_image() {
+    echo ""
+    echo "Testing Jupyter image..."
+    
+    echo -n "  Testing ipykernel import... "
+    VERSION=$(podman run --rm mcp-forge/jupyter:latest python -c "import ipykernel; print(ipykernel.__version__)")
+    echo "✓ ipykernel $VERSION"
+    
+    echo -n "  Testing kernel launcher... "
+    podman run --rm mcp-forge/jupyter:latest python -m ipykernel_launcher --help > /dev/null 2>&1
+    echo "✓ launcher works"
+}
+
+# Parse arguments
+ACTION="${1:-jupyter}"
+
+case "$ACTION" in
+    --all)
+        ensure_base_images
+        build_jupyter
+        verify_images
+        test_jupyter_image
+        ;;
+    --jupyter)
+        build_jupyter
+        test_jupyter_image
+        ;;
+    *)
+        echo "Usage: $0 [--all|--jupyter]"
+        echo ""
+        echo "  --all      Ensure base images and build Jupyter image"
+        echo "  --jupyter  Build Jupyter image only (default)"
+        exit 1
+        ;;
+esac
+
+echo ""
+echo "✓ Done!"