Add UI mode event log and audit trail

[wauputr4]

Goal

Give owners and contributors enough traceability to debug UI mode safely.

Scope

• Show recent workflow events: received message, orchestration result, ticket update, memory update, owner notification, private assistant handoff.
• Redact secrets and large raw payloads by default.
• Provide IDs for customer, ticket, message, event, and private agent job/result when available.
• Add filtering by customer/ticket/event type if simple.

Acceptance criteria

• Owner can inspect the last N UI mode events.
• Secret-like values are redacted in UI and logs.
• Event rows link or point to relevant customer/ticket IDs.
• Audit data is backed by existing storage or a documented minimal extension.