Add Geofence MVP feature implementation

Implemented complete MVP for geofencing functionality with database,
backend logic, MQTT integration, and API endpoints.

**Phase 1: Database & Core Logic**
- scripts/init-geofence-db.js: Database initialization for Geofence tables
- lib/types.ts: TypeScript types for Geofence, GeofenceEvent, GeofenceStatus
- lib/geofence-engine.ts: Core geofencing logic (Haversine distance, state tracking)
- lib/geofence-db.ts: Database layer with CRUD operations
- package.json: Added db:init:geofence script

**Phase 2: MQTT Integration & Email Notifications**
- emails/geofence-enter.tsx: React Email template for enter events
- emails/geofence-exit.tsx: React Email template for exit events
- lib/email-renderer.ts: Added geofence email rendering functions
- lib/geofence-notifications.ts: Notification service for geofence events
- lib/mqtt-subscriber.ts: Integrated automatic geofence checking on location updates

**Phase 3: Minimal API**
- app/api/geofences/route.ts: GET (list) and POST (create) endpoints
- app/api/geofences/[id]/route.ts: DELETE endpoint
- All endpoints with authentication and ownership checks

**MVP Simplifications:**
- No zone limit enforcement (unlimited for all users)
- No notification flags (always send Enter + Exit emails)
- Device assignment required (no NULL device logic)
- Circular geofences only

**Features:**
✅ Automatic geofence detection on MQTT location updates
✅ Email notifications for enter/exit events
✅ State tracking to prevent duplicate events
✅ REST API for geofence management
✅ Non-blocking async processing

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

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

package.json

@@ -8,9 +8,10 @@
     "build": "next build",
     "start": "next start",
     "lint": "next lint",
-    "db:init": "node scripts/init-database.js && node scripts/init-locations-db.js",
+    "db:init": "node scripts/init-database.js && node scripts/init-locations-db.js && node scripts/init-geofence-db.js",
     "db:init:app": "node scripts/init-database.js",
     "db:init:locations": "node scripts/init-locations-db.js",
+    "db:init:geofence": "node scripts/init-geofence-db.js",
     "db:cleanup": "node scripts/cleanup-old-locations.js",
     "db:cleanup:7d": "node scripts/cleanup-old-locations.js 168",
     "db:cleanup:30d": "node scripts/cleanup-old-locations.js 720",
@@ -45,6 +46,7 @@
   "devDependencies": {
     "@types/better-sqlite3": "^7.6.13",
     "@types/nodemailer": "^7.0.3",
+    "@types/uuid": "^10.0.0",
     "autoprefixer": "^10.4.22",
     "postcss": "^8.5.6",
     "tailwindcss": "^4.1.17"