Prepare web_hook_logs_daily table for multi-organization support

What does this MR do and why?

This MR enables the web_hook_logs_daily table to support GitLab's multi-organization architecture.

Currently, webhook logs don't have a way to identify which organization they belong to. As GitLab evolves to support multiple organizations, we need to ensure all data can be properly attributed and isolated by organization. This change makes that possible.

This is a necessary step toward Cells 1.0, which will allow GitLab to scale by distributing organizations across multiple database instances.

Related issue

Relates to #524820

MR acceptance checklist

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