Discovery: persist schema policy settings

[BadgerOps]

Follow-up to #193 and the network relationship/object work.

Summary

Persist the network schema policy as an operator setting instead of requiring callers to pass request-scoped query parameters on every merged network view or conflict request.

Why

CloudPAM now supports account-level, region-level, global, and manual schema policy evaluation through query parameters. Operators need a durable default so duplicate detection and hierarchy evidence are consistent across UI/API sessions and process restarts.

Scope

• Add a persisted schema policy setting using the existing settings storage path.
• Store policy fields such as name, ownership strategy, duplicate scope, hierarchy scope, and optional duplicate override.
• Use query parameters as per-request overrides; otherwise fall back to the persisted setting; otherwise use the conservative account-level default.
• Surface the active policy in merged network/conflict evidence and API responses where useful.
• Add docs for configuring and overriding schema policy.

Acceptance Criteria

• Operators can persist a default schema policy.
• Merged network views and conflict evaluation use the persisted policy when no query override is supplied.
• Query parameters still override the persisted policy for one request.
• Tests cover persisted default behavior, query override behavior, and fallback to account-level defaults when no setting exists.