feat(webhooks): add signing secret rotation endpoint

[gabrielmfern]

This adds resend.webhooks().rotateSigningSecret(webhookId) for POST /webhooks/{webhook_id}/signing-secret/rotate, mirroring the event replay method. The response model carries object, id, and signing_secret, the same shape create webhook already returns.

Spec: resend/resend-openapi#113
Linear: https://linear.app/resend/issue/DEV-2079

🤖 Generated with Claude Code

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Summary by cubic

Adds a new endpoint to rotate a webhook's signing secret. This lets users replace a compromised secret without recreating the webhook; the previous secret keeps working for 24 hours after rotation.

• Implements the signing secret rotation endpoint from DEV-2079, matching the existing replay event method and returning the same response shape as create webhook.
• Bumps the package version to 4.24.0.

^{Written for commit c4faa31. Summary will update on new commits.}

[klotty]

No issues found across 3 files

Confidence score: 5/5

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

<sub>Auto-approved: Adds a new webhook signing-secret rotation endpoint and response model, mirroring the existing replay method, with a test covering the new call.

Re-trigger cubic</sub>

[cubic-dev-ai]

0 issues found across 1 file (changes from recent commits).

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 webhook signing-secret rotation method and response model, expanding the SDK's public API surface with a new endpoint that needs human contract review.

Re-trigger cubic</sub>

[felipefreitag]

They aren't invalidated immediately, there's a 24-hour grace

[cubic-dev-ai]

0 issues found across 1 file (changes from recent commits).

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 signing-secret rotation endpoint and response model, expanding the SDK's API surface; a human should review the endpoint design and response shape before release.

Re-trigger cubic</sub>