🛠️ feat: add automated Heroku-24 migration script (#180)

Add automated migration script to handle Heroku-22 to Heroku-24 upgrade:

- Add scripts/migrate-heroku-24.sh: Automated migration script
  - Handles migration with safety checks and backups
  - Includes automatic rollback capability
  - Performs smoke tests after migration
  - Detailed logging and error handling

- Add scripts/README-heroku-migration.md: Complete documentation
  - Usage instructions and examples
  - Features and safety mechanisms
  - Troubleshooting guide
  - Post-migration monitoring instructions

Features:
✅ Automatic database and config backups
✅ Maintenance mode handling
✅ Built-in smoke tests
✅ One-command rollback
✅ Confirmation prompts
✅ Detailed logging

Related to #180

Author: matrixise

scripts/README-heroku-migration.md

@@ -0,0 +1,244 @@
+# Heroku-24 Migration Script
+
+Automated script to migrate the Python Ireland website from Heroku-22 to Heroku-24 stack, with built-in rollback capabilities.
+
+## Prerequisites
+
+- Heroku CLI installed and authenticated (`heroku login`)
+- Git repository with `heroku` remote configured
+- Access to the `pythonie` Heroku app
+- HEROKU_APP environment variable set (or defaults to `pythonie`)
+
+## Quick Start
+
+### 1. Check Current Status
+
+```bash
+./scripts/migrate-heroku-24.sh status
+```
+
+This shows:
+- Current stack (heroku-22 or heroku-24)
+- Available stacks
+- PostgreSQL version and status
+- Migration readiness
+
+### 2. Run Migration
+
+```bash
+./scripts/migrate-heroku-24.sh migrate
+```
+
+**What happens:**
+1. Creates database and config backups
+2. Enables maintenance mode (~5-10 min downtime)
+3. Upgrades stack to heroku-24
+4. Redeploys the application
+5. Runs smoke tests (homepage, admin, logs)
+6. Disables maintenance mode
+7. Reports success or offers rollback
+
+### 3. Rollback (if needed)
+
+```bash
+./scripts/migrate-heroku-24.sh rollback
+```
+
+**What happens:**
+1. Enables maintenance mode
+2. Rolls back to previous Heroku release
+3. Reverts stack to heroku-22
+4. Redeploys the application
+5. Disables maintenance mode
+
+## Features
+
+### ✅ Safety Features
+
+- **Automatic backups**: Database and config saved before migration
+- **Confirmation prompts**: Requires explicit confirmation before proceeding
+- **Maintenance mode**: App goes into maintenance during migration
+- **Smoke tests**: Automatic verification after migration
+- **Error handling**: Stops on errors, offers rollback option
+- **Detailed logging**: All actions logged to timestamped file
+
+### 📋 Migration Steps
+
+The script performs these steps automatically:
+
+1. **Setup & Verification**
+   - Checks Heroku CLI is installed
+   - Verifies authentication
+   - Confirms app exists
+
+2. **Backup Phase**
+   - Creates PostgreSQL backup
+   - Saves configuration to file
+   - Downloads backup locally
+
+3. **Migration Phase**
+   - Enables maintenance mode
+   - Creates final backup
+   - Upgrades stack to heroku-24
+   - Redeploys application
+
+4. **Verification Phase**
+   - Waits for deployment stabilization
+   - Tests homepage accessibility
+   - Tests admin accessibility
+   - Checks logs for errors
+
+5. **Completion**
+   - Disables maintenance mode
+   - Reports success
+   - Provides monitoring instructions
+
+## Usage Examples
+
+### Basic migration (uses default app: pythonie)
+
+```bash
+./scripts/migrate-heroku-24.sh migrate
+```
+
+### Migration for different app
+
+```bash
+HEROKU_APP=my-other-app ./scripts/migrate-heroku-24.sh migrate
+```
+
+### Check status before migration
+
+```bash
+./scripts/migrate-heroku-24.sh status
+```
+
+### Emergency rollback
+
+```bash
+./scripts/migrate-heroku-24.sh rollback
+```
+
+## Output & Logging
+
+All actions are logged to:
+```
+/tmp/heroku-migration-backups/migration-YYYYMMDD-HHMMSS.log
+```
+
+Backups are saved to:
+```
+/tmp/heroku-migration-backups/backup-YYYYMMDD-HHMMSS.dump
+/tmp/heroku-migration-backups/config-YYYYMMDD-HHMMSS.env
+```
+
+## What to Monitor After Migration
+
+### Immediate (0-1 hour)
+
+```bash
+# Watch logs in real-time
+heroku logs --tail -a pythonie
+
+# Check dyno status
+heroku ps -a pythonie
+
+# Verify stack
+heroku stack -a pythonie
+```
+
+### Short-term (1-24 hours)
+
+```bash
+# Check metrics
+heroku metrics -a pythonie
+
+# Review error rates
+heroku logs -a pythonie | grep -i error
+
+# Test critical features
+# - Homepage: https://python.ie
+# - Admin: https://python.ie/admin/
+# - Content pages
+```
+
+### Medium-term (24-48 hours)
+
+- Monitor error logs daily
+- Check performance metrics
+- Verify all business features
+- Review CPU/memory usage
+
+## Troubleshooting
+
+### Migration fails during redeploy
+
+The script will automatically offer to rollback. Accept the rollback prompt.
+
+### Smoke tests fail
+
+The script will ask if you want to rollback. You can:
+- Accept rollback (recommended)
+- Decline and debug manually (app stays in maintenance mode)
+
+### Manual rollback needed
+
+```bash
+# Enable maintenance
+heroku maintenance:on -a pythonie
+
+# Rollback release
+heroku rollback -a pythonie
+
+# Revert stack
+heroku stack:set heroku-22 -a pythonie
+git push heroku master
+
+# Disable maintenance
+heroku maintenance:off -a pythonie
+```
+
+### App won't start after migration
+
+1. Check build logs:
+   ```bash
+   heroku logs --tail -a pythonie
+   ```
+
+2. Check for migration errors:
+   ```bash
+   heroku run python pythonie/manage.py showmigrations -a pythonie
+   ```
+
+3. Rollback if needed:
+   ```bash
+   ./scripts/migrate-heroku-24.sh rollback
+   ```
+
+## Exit Codes
+
+- `0` - Success
+- `1` - Error occurred (check logs)
+
+## Environment Variables
+
+- `HEROKU_APP` - Heroku application name (default: `pythonie`)
+
+## Security Notes
+
+- Backups contain sensitive data - stored in `/tmp` (auto-cleaned on reboot)
+- Config files contain secrets - handle with care
+- Clean up old backups regularly
+
+## Support
+
+For issues or questions:
+- See full test documentation: `docs/heroku-24-migration-tests.md`
+- GitHub issue: #180
+- Heroku support: https://help.heroku.com/
+
+## Related Documentation
+
+- [Heroku-24 Stack](https://devcenter.heroku.com/articles/heroku-24-stack)
+- [Stack Upgrades](https://devcenter.heroku.com/articles/upgrading-to-the-latest-stack)
+- [Python 3.13 on Heroku](https://devcenter.heroku.com/articles/python-support)