WebhookDelivery and WebhookDeliveryAttempt objects

Goal

Define the WebhookDelivery and WebhookDeliveryAttempt objects within the shared-types folder.

Proposed Solution

Add WebhookDeliveryAttempts. WebhookDelivery objects as a first step for #[ISSUE]

The objects would roughly look like this - however it is okay for the implemetation to differ if there are any other ideas. We should add comments similar to other types in the shared-types folder:

export interface WebhookDelivery {
  id: string;
  event_id: string;
  webhook_endpoint_id: string;
  status: 'pending' | 'retrying' | 'succeeded' | 'failed';
  next_attempt_at: number | null;
  delivered_at: number | null;
  claim_until: number | null;
  attempts: WebhookDeliveryAttempt[];
}

export interface WebhookDeliveryAttempt {
  attempt_number: number;
  attempted_at: number;
  completed_at: number;
  result: 'succeeded' | 'http_error' | 'timed_out' | 'network_error';
  http_status: number | null;
  duration_ms: number;
  error: string | null;
  url: string;
}

A recovered delivery attempt might look like this:

{
  "id": "whd_z_123",
  "event_id": "evt_z_123",
  "webhook_endpoint_id": "we_z_123",
  "status": "succeeded",
  "next_attempt_at": null,
  "delivered_at": 1789240915,
  "claim_until": null,
  "attempts": [
    {
      "attempt_number": 1,
      "attempted_at": 1789237274,
      "completed_at": 1789237278,
      "result": "http_error",
      "http_status": 500,
      "duration_ms": 3693,
      "error": "HTTP 500",
      "url": "https://example.com/webhooks"
    },
    {
      "attempt_number": 2,
      "attempted_at": 1789240915,
      "completed_at": 1789240918,
      "result": "succeeded",
      "http_status": 200,
      "duration_ms": 3206,
      "error": null,
      "url": "https://example.com/webhooks"
    }
  ]
}

Acceptance criteria

• All tests still pass
• The objects are added to the shared-types folder with the correct comments.
• The objects are well defined with the goal of completing [Epic] Webhook retry system #172.
• Only these new types are added to the shared-types folder, no other changes are required.