Self-hosting license management

TofuPilot now handles license validation, plan enforcement, and usage tracking for self-hosted instances directly in the dashboard.

• Added feature-based license gating. SSO, SCIM, and Teams are now tied to your plan tier and enforced at runtime.
• Built a self-hosted usage page showing station count, user count, and monthly runs against plan limits.
• Added air-gapped license activation for instances without internet access.
• License card on the plan page shows current plan, limits, and expiry at a glance.
• Fixed station duplicate check and limit-reached modal that blocked test uploads silently.