refactor: revert CI image approach and use standard npm ci in workflows

The CI image approach with pre-installed dependencies doesn't work with Gitea Actions due to workspace mounting issues. When Gitea Actions runs a container job, it mounts the workspace at a specific path (e.g., /workspace/david/euchre_camp), which hides the container's /app directory where dependencies were installed.

Changes:
- Reverted pr.yml unit-tests to use node:20-alpine with npm ci
- Updated pr.yml acceptance-tests to use mcr.microsoft.com/playwright image with npm ci
- Updated test.yml to use node:20-alpine with npm ci
- Removed ci-image-builder.yml workflow
- Removed Dockerfile.ci and build-ci-image.sh
- Updated AGENTS.md and README.md to document the deprecation
- Updated justfile to remove CI image commands

The standard approach of running npm ci in each workflow is the recommended approach for Gitea Actions.

scripts/build-ci-image.sh

@@ -1,44 +0,0 @@
-#!/bin/bash
-# Build and test the CI runner image locally
-
-set -e
-
-IMAGE_NAME="euchre-camp-ci-runner"
-TAG="${1:-latest}"
-
-echo "Building CI runner image..."
-echo "Image: ${IMAGE_NAME}:${TAG}"
-echo ""
-
-# Build the image
-docker build \
-    -f Dockerfile.ci \
-    -t ${IMAGE_NAME}:${TAG} \
-    .
-
-echo ""
-echo "✅ Image built successfully!"
-echo ""
-
-# Test the image
-echo "Testing CI image..."
-docker run --rm ${IMAGE_NAME}:${TAG} sh -c "
-    echo 'Node.js version:' && node --version
-    echo 'npm version:' && npm --version
-    echo 'Git version:' && git --version
-    echo 'Prisma version:' && npx prisma --version
-    echo ''
-    echo 'Installed packages (top 10):'
-    npm list --depth=0 | head -10
-"
-
-echo ""
-echo "✅ CI image is ready to use!"
-echo ""
-echo "To use in GitHub Actions/Gitea Actions:"
-echo "  container:"
-echo "    image: docker.notsosm.art/${IMAGE_NAME}:${TAG}"
-echo ""
-echo "To push to registry:"
-echo "  docker tag ${IMAGE_NAME}:${TAG} docker.notsosm.art/${IMAGE_NAME}:${TAG}"
-echo "  docker push docker.notsosm.art/${IMAGE_NAME}:${TAG}"