feat(admin-web): add autoban policy settings

[dinoallo]

Background

PR 94 added the admin-side autoban policy and namespace locking flow. Admin Web could only manage it through the generic raw JSON config page, so operators had no focused UI for enabling the policy or maintaining process-name rules.

Changes

• Add an Autoban page under Admin Web with navigation and overview quick-link entry points.
• Add form controls for enabled/dry-run state, source selection, operator/reason metadata, namespace allow/deny lists, and process-name allow/deny lists.
• Save the canonical autoban_policy project config while still reading an existing same-type fallback config for migration visibility.
• Show a live JSON preview of the policy that will be written to the backend.

Risks / Notes

• Backend behavior is unchanged; the page writes the existing project config API used by the autoban service.
• If an older noncanonical autoban_policy-type config exists, the page reads it but saves future changes to config_name=autoban_policy.

Links

Follows #94