apollo-webhooks-events

# Apollo Webhooks Events

## Overview
Implement webhook handlers for Apollo.io to receive real-time notifications about contact updates, sequence events, and engagement activities.

## Apollo Webhook Events

| Event Type | Description | Payload Contains |
|------------|-------------|------------------|
| `contact.created` | New contact added | Contact data |
| `contact.updated` | Contact info changed | Updated fields |
| `sequence.started` | Contact added to sequence | Sequence & contact IDs |
| `sequence.completed` | Sequence finished | Completion status |
| `email.sent` | Email delivered | Email & contact info |
| `email.opened` | Email was opened | Open timestamp |
| `email.clicked` | Link clicked | Click details |
| `email.replied` | Reply received | Reply content |
| `email.bounced` | Email bounced | Bounce reason |

## Webhook Handler Implementation

### Express Handler
```typescript
// src/routes/webhooks/apollo.ts
import { Router } from 'express';
import crypto from 'crypto';
import { z } from 'zod';

const router = Router();

// Webhook payload schemas
const ContactEventSchema = z.object({
  event: z.enum(['contact.created', 'contact.updated']),
  timestamp: z.string(),
  data: z.object({
    contact: z.object({
      id: z.string(),
      email: z.string().optional(),
      name: z.string().optional(),
      title: z.string().optional(),
      organization: z.object({
        name: z.string(),
      }).optional(),
    }),
    changes: z.record(z.any()).optional(),
  }),
});

const SequenceEventSchema = z.object({
  event: z.enum(['sequence.started', 'sequence.completed', 'sequence.paused']),
  timestamp: z.string(),
  data: z.object({
    sequence_id: z.string(),
    contact_id: z.string(),
    status: z.string().optional(),
  }),
});

const EmailEventSchema = z.object({
  event: z.enum(['email.sent', 'email.opened', 'email.clicked', 'email.replied', 'email.bounced']),
  timestamp: z.string(),
  data: z.object({
    email_id: z.string(),
    contact_id: z.