feat(webhooks): add event replay endpoint

[gabrielmfern]

Adds Resend::Webhooks.replay_event(webhook_id, event_id), which calls POST /webhooks/{webhook_id}/events/{event_id}/replay and returns { object: "webhook_event", id: "msg_..." }. Queues one more delivery of the event to the webhook; manual replays do not schedule automatic retries.

replayed = Resend::Webhooks.replay_event(
  "4dd369bc-aa82-4ff3-97de-514ae3000ee0",
  "msg_1srOrx2ZWZBpBUvZwXKQmoEYga2"
)
puts replayed[:id]

Also adds the call to examples/webhooks.rb and sets Metrics/ModuleLength: 169 in .rubocop.yml. The Webhooks module is a flat list of one-method-per-endpoint wrappers, so its length tracks the API surface; the default 100 was crossed by this method and would be crossed again by the next one.

Spec PR: resend/resend-openapi#112
API PR: https://github.com/resend/resend-monorepo/pull/9535

Checks (Ruby 4.0.6, bundle install): bundle exec rubocop no offenses, bundle exec rake spec 400 examples, 0 failures. No live API call was made; version bump left for the chore PR.

Part of DEV-2005.

Linear: https://linear.app/resend/issue/DEV-2011

[cubic-dev-ai]

No issues found across 4 files

Confidence score: 5/5

• Automated review surfaced no issues in the provided summaries.
• No files require special attention.

<sub>Requires human review: Adds a new public webhook replay API that triggers an additional event delivery. Human approval is needed for the external contract and operational semantics of manual replays.

Re-trigger cubic</sub>

[cubic-dev-ai]

All reported issues were addressed across 1 file (changes from recent commits).

<sub>Reply with feedback, questions, or to request a fix.

Re-trigger cubic</sub>