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>

lib/email-renderer.ts

@@ -5,6 +5,8 @@ import { render } from '@react-email/components';
 import WelcomeEmail from '@/emails/welcome';
 import PasswordResetEmail from '@/emails/password-reset';
 import MqttCredentialsEmail from '@/emails/mqtt-credentials';
+import GeofenceEnterEmail from '@/emails/geofence-enter';
+import GeofenceExitEmail from '@/emails/geofence-exit';
 
 export interface WelcomeEmailData {
   username: string;
@@ -28,6 +30,17 @@ export interface MqttCredentialsEmailData {
   brokerPort?: string;
 }
 
+export interface GeofenceEmailData {
+  username: string;
+  deviceName: string;
+  geofenceName: string;
+  timestamp: string;
+  latitude: number | string;
+  longitude: number | string;
+  distanceFromCenter: number;
+  mapUrl?: string;
+}
+
 export async function renderWelcomeEmail(data: WelcomeEmailData): Promise<string> {
   return render(WelcomeEmail(data));
 }
@@ -40,6 +53,14 @@ export async function renderMqttCredentialsEmail(data: MqttCredentialsEmailData)
   return render(MqttCredentialsEmail(data));
 }
 
+export async function renderGeofenceEnterEmail(data: GeofenceEmailData): Promise<string> {
+  return render(GeofenceEnterEmail(data));
+}
+
+export async function renderGeofenceExitEmail(data: GeofenceEmailData): Promise<string> {
+  return render(GeofenceExitEmail(data));
+}
+
 export async function renderEmailTemplate(
   template: string,
   data: any
@@ -51,6 +72,10 @@ export async function renderEmailTemplate(
       return renderPasswordResetEmail(data);
     case 'mqtt-credentials':
       return renderMqttCredentialsEmail(data);
+    case 'geofence-enter':
+      return renderGeofenceEnterEmail(data);
+    case 'geofence-exit':
+      return renderGeofenceExitEmail(data);
     default:
       throw new Error(`Unknown email template: ${template}`);
   }