[US-027] Feature flags management

[leimo2011]

User Story

As a super admin,
I want to toggle platform features on/off without code deployments,
So that I can control rollouts and respond to incidents instantly.

Acceptance Criteria

• Feature flag list with name, description, status (on/off), environments (dev/staging/prod)
• Toggle feature flag with confirmation dialog
• Per-region flags (e.g., enable a feature only in KW)
• Per-user-percentage rollout (e.g., 10% of users)
• Mobile app respects flags within 60 seconds of change

Estimate: 5 SP | Milestone: M3

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Epic: [EPIC-12] Super Admin Panel