User Story: Station Bot runtime safety and feature flags

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User Story

As a Station super admin, I need to manage Station-Bot runtime safety and feature flags so that I can control read-only mode and the major bot feature gates from Station.

Definition of Done

• Station exposes BOT_READ_ONLY_MODE, VERIFICATION_ENABLED, MANUFACTURING_ENABLED, NOMINATION_DIGEST_ENABLED, EVENT_REMINDERS_ENABLED, EXEC_HANGAR_ENABLED, and STATION_TIMER_ENABLED
• Validation 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 toggle read-only mode and the major runtime feature flags from Station
• The saved values persist on reload
• Guild-scoped admins cannot access these controls

Technical Elaboration

This ticket covers runtime safety and feature-gate flags only. It is separate from verification throttles, RSI tuning, event-reminder cleanup, database/TLS, and logging settings.

Design Elaboration

This screen should emphasize operational consequences. Read-only mode should be especially prominent because it changes the behavior of the broader admin surface.

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