fix: version bumping and Docker registry authentication (#17)

## Summary

This PR fixes the release workflow to properly handle version bumping on PR merge and uses the new Docker registry authentication secrets.

## Changes

### Release Workflow (release.yml)
- **Version Bumping**: Now automatically bumps version on PR merge
  - Determines bump type from commit messages (major/minor/patch)
  - Commits version bump to `package.json` and `CHANGELOG.md`
  - Creates git tag for the release
- **Docker Registry Auth**: Uses `DOCKER_LOGIN` and `DOCKER_PASSWORD` secrets
  - Falls back gracefully if secrets are not configured
- **Tag Handling**: Checks if tag exists before creating (prevents failures)

### PR Workflow (pr.yml) - NEW
- Runs unit tests on every PR
- Analyzes commits to suggest bump type
- Comments the suggested bump type on the PR

### Documentation
- Added `WORKFLOW_ARCHITECTURE.md` explaining the workflow design

## Workflow Architecture

**Two-step process:**
1. **PR Workflow** (on PR): Analyzes commits and suggests bump type
2. **Release Workflow** (on merge): Bumps version, creates tag, builds Docker image

## Benefits

1. **No CI Loops**: Version bump commits are detected and skipped
2. **Clear Communication**: PR comments inform developers of version impact
3. **Semantic Versioning**: Automated adherence to semver rules
4. **Traceability**: Git tags and changelog reflect all changes

## Testing

The new workflows will be tested when this PR is merged.

Closes #13 (Add database test safety configuration)

Reviewed-on: #17
Co-authored-by: David Gwilliam <dhgwilliam@gmail.com>
Co-committed-by: David Gwilliam <dhgwilliam@gmail.com>

scripts/run-tests-in-container.sh

@@ -0,0 +1,15 @@
+#!/bin/bash
+# Run tests in a Node.js container (for consistent environment)
+
+set -e
+
+echo "Running tests in node:20-alpine container..."
+echo "This avoids Node.js setup time and ensures consistent environment."
+echo ""
+
+# Run unit tests in container
+docker run --rm \
+  -v "$(pwd):/app" \
+  -w /app \
+  node:20-alpine \
+  sh -c "apk add --no-cache bash git && npm ci && npm run test:run"