[Task] v1 publishing detail: expose bundle/publish start/end timestamps

Context

Surfaced by the Publishing Queue migration spike (#36039). The new Bundle Details modal (per the redesign) renders a 9-field definition list, four of which depend on backend fields:

• Bundle start
• Bundle end
• Publish start
• Publish end

com.dotcms.rest.api.v1.publishing.PublishingResource#getPublishingJobDetails (PublishingResource:331) currently returns PublishingJobDetailView, which exposes status, created/modified, environments, and endpoint breakdown — but not the publish window timestamps. The Bundle entity has publishDate and expireDate, but the helper that builds the view does not include them.

Proposed change

Add to PublishingJobDetailView:

private final Date bundleStart;   // bundling started (from PublishAuditStatus)
private final Date bundleEnd;     // bundling finished
private final Date publishStart;  // first push attempt
private final Date publishEnd;    // last endpoint completion (or null if still sending)

Populate from existing audit data + bundle entity in the helper.

Acceptance criteria

• GET /v1/publishing/{bundleId} JSON includes the four new ISO8601 timestamps (bundle_start, bundle_end, publish_start, publish_end)
• Null when not yet known (e.g. publish_end is null until the last endpoint reports)
• OpenAPI schema updated
• Integration test asserts the fields are present and correctly populated for a completed and an in-progress bundle

Source links

• Spike audit: #36039
• FE consumer: #36040 (Bundle Details modal expects all four fields)
• Epic: #34734

Start at PublishingResource#getPublishingJobDetails (PublishingResource:331) and inspect PublishingJobDetailView, the Bundle entity, and existing PublishAuditStatus data used by the helper. Check the OpenAPI schema and integration-test coverage for GET /v1/publishing/{bundleId}. Done means completed and in-progress bundles return the four ISO8601 fields, with unknown values represented as null.