User Story: Station Bot logging level and external sink controls

[GitAddRemote]

User Story

As a Station super admin, I need to manage Station-Bot logging controls so that I can tune log verbosity, file logging behavior, and external sink configuration from Station.

Definition of Done

• Station exposes LOG_LEVEL, LOG_FILE_ENABLED, and ELASTICSEARCH_NODE
• Validation, masking where appropriate, and save/reload flows are covered by tests
• Guild owners/admins cannot access these controls
• pnpm typecheck passes

Acceptance Criteria

• A station_super_admin can update logging controls from Station
• Invalid values are rejected with field-level validation
• Guild-scoped admins cannot access these controls

Technical Elaboration

This ticket covers logging-level and external-sink configuration only. It is separate from database/TLS and other runtime controls.

Design Elaboration

This UI should communicate that these settings affect observability behavior and may have operational cost or noise implications.

---

Parent Epic: #231
Depends on: #232, #233, #242