Handle repository persistence failures in Publisher service

[Copilot]

• Add error handling for update() failures in publish() method
• Add error handling for update() failures in unpublish() method
• Add error handling for update() failures in schedule() method
• Verify PHP syntax is correct
• Reply to review comment with commit hash
• Fix broken tests by configuring mock return values
• Add new tests for persistence failure scenarios
• Verify tests pass in CI

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[ljonesfl]

@copilot can you take a look at the broken tests in the GitHub actions?