Add AI usage collection to namespace settings table

What does this MR do and why?

This MR adds AI usage collection setting to namespace settings.

Up

bin/rails db:migrate:up:main VERSION=20260202134241
main: == [advisory_lock_connection] object_id: 133840, pg_backend_pid: 37725
main: == 20260202134241 AddAiUsageDataCollectionToNamespaceAiSettings: migrating ====
main: -- add_column(:namespace_ai_settings, :ai_usage_data_collection_enabled, :boolean, {:default=>false, :null=>false})
main:    -> 0.0519s
main: == 20260202134241 AddAiUsageDataCollectionToNamespaceAiSettings: migrated (0.0800s) 

main: == [advisory_lock_connection] object_id: 133840, pg_backend_pid: 37725

Down

bin/rails db:migrate:down:main VERSION=20260202134241
main: == [advisory_lock_connection] object_id: 133820, pg_backend_pid: 37152
main: == 20260202134241 AddAiUsageDataCollectionToNamespaceAiSettings: reverting ====
main: -- remove_column(:namespace_ai_settings, :ai_usage_data_collection_enabled)
main:    -> 0.0614s
main: == 20260202134241 AddAiUsageDataCollectionToNamespaceAiSettings: reverted (0.0894s) 

main: == [advisory_lock_connection] object_id: 133820, pg_backend_pid: 37152

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Before	After

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