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/types.ts

@@ -28,3 +28,89 @@ export interface Device {
   name: string;
   color: string;
 }
+
+// Geofence types
+export interface Geofence {
+  id: string;
+  name: string;
+  description: string | null;
+
+  // Geometry
+  shape_type: 'circle';
+  center_latitude: number;
+  center_longitude: number;
+  radius_meters: number;
+
+  // Assignment
+  owner_id: string;
+  device_id: string;
+
+  // Status & Metadata
+  is_active: number; // 0 or 1
+  color: string;
+
+  // Timestamps
+  created_at: string;
+  updated_at: string;
+}
+
+export interface GeofenceEvent {
+  id?: number;
+  geofence_id: string;
+  device_id: string;
+  location_id: number;
+
+  // Event details
+  event_type: 'enter' | 'exit';
+  latitude: number | string;
+  longitude: number | string;
+
+  // Metadata
+  distance_from_center: number | null;
+  notification_sent: number; // 0 = pending, 1 = sent, 2 = failed
+  notification_error: string | null;
+
+  // Timestamps
+  timestamp: string;
+  created_at?: string;
+}
+
+export interface GeofenceStatus {
+  id?: number;
+  device_id: string;
+  geofence_id: string;
+
+  // Current status
+  is_inside: number; // 0 or 1
+  last_enter_time: string | null;
+  last_exit_time: string | null;
+  last_checked_at: string | null;
+
+  // Timestamps
+  created_at?: string;
+  updated_at?: string;
+}
+
+// Input types for creating/updating geofences
+export interface CreateGeofenceInput {
+  id: string;
+  name: string;
+  description?: string;
+  center_latitude: number;
+  center_longitude: number;
+  radius_meters: number;
+  owner_id: string;
+  device_id: string;
+  color?: string;
+}
+
+export interface CreateGeofenceEventInput {
+  geofence_id: string;
+  device_id: string;
+  location_id: number;
+  event_type: 'enter' | 'exit';
+  latitude: number | string;
+  longitude: number | string;
+  distance_from_center: number;
+  timestamp: string;
+}