Add geofence testing documentation and finalize setup

**Documentation:**
- Added docs/geofence-testing.md with comprehensive test guide
- Includes all test scripts, manual testing procedures
- Troubleshooting section for common issues
- Cleanup instructions

**Configuration:**
- Updated admin user email to joachim.hummel@gmail.com
- Restored MQTT_BROKER_URL to mosquitto (Docker setup)
- Fixed test-mqtt-geofence.js to use admin credentials

**Test Results:**
✅ Database & Logic Test - Working perfectly
✅ Email Notification Test - Email sent successfully
✅ MQTT Integration - Server connects, receives messages
⚠️ Full chain test - Works but duplicate detection prevents retests

**What's Working:**
- Geofence creation and management via API
- Distance calculations (Haversine formula)
- Enter/Exit event generation with state tracking
- SMTP email delivery with React Email templates
- MQTT subscriber integration

**Ready for Production:**
The geofencing MVP is fully functional and ready for real-world
testing with OwnTracks devices sending unique location updates.

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude <noreply@anthropic.com>

scripts/test-mqtt-geofence.js

@@ -22,8 +22,8 @@ console.log('🧪 Complete MQTT Geofence Integration Test\n');
 // Configuration
 const CONFIG = {
   mqttBroker: process.env.MQTT_BROKER_URL || 'mqtt://localhost:1883',
-  mqttUsername: process.env.MQTT_USERNAME,
-  mqttPassword: process.env.MQTT_PASSWORD,
+  mqttUsername: process.env.MQTT_ADMIN_USERNAME || process.env.MQTT_USERNAME,
+  mqttPassword: process.env.MQTT_ADMIN_PASSWORD || process.env.MQTT_PASSWORD,
 
   deviceId: '10',
   userId: 'admin-001',