feat: add Healthchecks Cloudron package (Monitoring)

- Create Dockerfile wrapping official Healthchecks image
- Add CloudronManifest.json with PostgreSQL addon
- Create start.sh script with PostgreSQL wait and Django migrations
- Include README.md with comprehensive monitoring documentation
- Add .env.example for environment configuration
- Add CHANGELOG.md for version tracking
- Add logo.png (Healthchecks branding)

Healthchecks is a cron job monitoring service that listens
for HTTP requests and email messages (pings) from your cron
jobs and sends alerts when pings are late.

Package includes:
- Official Healthchecks Docker image wrapper (105MB)
- Cloudron PostgreSQL addon for Django database
- Automatic database migrations on startup
- Superuser creation via environment variables
- Email configuration support for alerts
- Comprehensive documentation with monitoring examples
- Examples for cron, systemd, scripts, and webhook monitoring

Features supported:
- Cron job monitoring via HTTP pings
- 25+ notification integrations (Email, SMS, Slack, Telegram, Matrix, etc.)
- Live-updating web dashboard
- Status badges for public monitoring
- Team management (projects, team members, read-only access)
- Monthly email reports
- WebAuthn 2FA support
- Tag-based organization
- Project grouping
- Detailed event logs
- Grace time configuration
- Cron expression support

Environment variables:
- SECRET_KEY: Django secret key
- ALLOWED_HOSTS: Allowed hosts (default: *)
- SITE_ROOT: Site root URL
- EMAIL_HOST/PORT/USER/PASSWORD: SMTP configuration
- SUPERUSER_EMAIL/PASSWORD: Admin account creation

Ports:
- 8000: Main HTTP port (web interface and API)

💘 Generated with Crush

Assisted-by: GLM-4.7 via Crush <crush@charm.land>

Package-Workspace/Monitoring/healthchecks/start.sh

@@ -0,0 +1,65 @@
+#!/bin/bash
+
+set -e
+
+echo "Starting Healthchecks Cloudron package..."
+
+# Database connection from Cloudron
+DB_NAME=${CLOUDRON_POSTGRESQL_DATABASE:-healthchecks}
+DB_USER=${CLOUDRON_POSTGRESQL_USERNAME:-hc}
+DB_PASSWORD=${CLOUDRON_POSTGRESQL_PASSWORD}
+DB_HOST=${CLOUDRON_POSTGRESQL_HOST:-127.0.0.1}
+DB_PORT=${CLOUDRON_POSTGRESQL_PORT:-5432}
+
+echo "Database host: $DB_HOST"
+echo "Database port: $DB_PORT"
+echo "Database name: $DB_NAME"
+
+# Wait for PostgreSQL to be ready
+echo "Waiting for PostgreSQL to be ready..."
+until PGPASSWORD=$DB_PASSWORD psql -h "$DB_HOST" -p "$DB_PORT" -U "$DB_USER" -d "$DB_NAME" -c '\q' 2>/dev/null; do
+  echo "PostgreSQL is unavailable - sleeping"
+  sleep 2
+done
+
+echo "PostgreSQL is ready!"
+
+# Django configuration
+export DEBUG=False
+export SECRET_KEY=${SECRET_KEY:-cloudron-secret-key-change-in-production}
+export ALLOWED_HOSTS=${ALLOWED_HOSTS:-'*'}
+export SITE_ROOT=${SITE_ROOT:-https://$CLOUDRON_APP_DOMAIN}
+export EMAIL_HOST=${EMAIL_HOST:-}
+export EMAIL_PORT=${EMAIL_PORT:-587}
+export EMAIL_HOST_USER=${EMAIL_HOST_USER:-}
+export EMAIL_HOST_PASSWORD=${EMAIL_HOST_PASSWORD:-}
+export EMAIL_USE_TLS=${EMAIL_USE_TLS:-True}
+export DEFAULT_FROM_EMAIL=${DEFAULT_FROM_EMAIL:-healthchecks@$CLOUDRON_APP_DOMAIN}
+
+# Database configuration
+export DB=postgresql
+export DB_HOST=$DB_HOST
+export DB_NAME=$DB_NAME
+export DB_USER=$DB_USER
+export DB_PASSWORD=$DB_PASSWORD
+export DB_PORT=$DB_PORT
+export DB_CONN_MAX_AGE=60
+
+# Run Django migrations
+echo "Running Django migrations..."
+python /opt/healthchecks/manage.py migrate --noinput
+
+# Collect static files
+echo "Collecting static files..."
+python /opt/healthchecks/manage.py collectstatic --noinput
+
+# Create superuser if specified
+if [ -n "$SUPERUSER_EMAIL" ] && [ -n "$SUPERUSER_PASSWORD" ]; then
+  echo "Creating superuser..."
+  echo "from django.contrib.auth import get_user_model; User = get_user_model(); User.objects.create_superuser('$SUPERUSER_EMAIL', '', '$SUPERUSER_PASSWORD')" | \
+    python /opt/healthchecks/manage.py shell || echo "Superuser may already exist"
+fi
+
+# Start Healthchecks
+echo "Starting Healthchecks..."
+exec uwsgi /opt/healthchecks/docker/uwsgi.ini