Frontend: Station Bot automation administration for purge jobs and event reminders

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User Story

As a guild administrator, I need Station-Bot scheduled automation administration split into focused stories so purge scheduling and event-reminder settings can be implemented separately and safely.

Definition of Done

• Temporary-member purge scheduling is delivered in User Story: Station Bot temporary-member purge scheduling #260
• Event reminder delivery configuration is delivered in User Story: Station Bot event reminder delivery configuration #262
• Event reminder cleanup and retention controls are delivered in User Story: Station Bot event reminder cleanup and retention controls #263
• This umbrella issue remains a parent/checklist only and does not duplicate child implementation scope

Acceptance Criteria

• The automation domain is fully represented by child issues User Story: Station Bot temporary-member purge scheduling #260, User Story: Station Bot event reminder delivery configuration #262, and User Story: Station Bot event reminder cleanup and retention controls #263
• Guild-scoped reminder delivery and operator-scoped cleanup are separated in the child stories
• Completing all child issues satisfies the automation configuration scope for this epic

Technical Elaboration

This issue now tracks the automation domain only. Direct implementation has been split into:

• User Story: Station Bot temporary-member purge scheduling #260 temporary-member purge scheduling
• User Story: Station Bot event reminder delivery configuration #262 event reminder delivery configuration
• User Story: Station Bot event reminder cleanup and retention controls #263 event reminder cleanup and retention controls

Design Elaboration

Automation should still feel schedule-centric in the final product, but the work is intentionally split so expiration logic, reminder delivery, and cleanup retention can each be validated independently.

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Parent Epic: #231
Child Issues: #260, #262, #263
Depends on: #232, #233, #242