feat(subscription): add subscription benefit plan management

[Glorhop]

📝 Background

This PR introduces a benefit-plan based subscription management model designed to improve admin-side operational efficiency and ensure data consistency across the platform.

🚀 What’s Included

1. Core Domain Models

• Benefit Package: Reusable package grouping specific permissions/groups and lease durations.
• Benefit Plan: A higher-level model composed of multiple benefit packages.
• User-Plan Assignment: Tracks active plan status per user (strictly one active plan per user).
• Database Schema: Migration tables and optimized indexes for the new models.

2. Admin APIs & Logic

• CRUD Operations: Full management endpoints for Benefit Packages and Benefit Plans.
• Membership Management:
  • List members of a specific plan.
  • Bulk assign/remove users to/from a plan.
  • Individual user plan assignment (get/set).
• Reconciliation: Automated subscription reconciliation flow triggered after plan or package updates.
• Cache Integrity: Cache invalidation hooks to ensure affected users/groups receive real-time updates.

3. Frontend Integration

• Updated API clients to support new subscription endpoints.
• New TypeScript types and i18n localization strings.
• Enhanced subscription admin views for better UX.

✨ Why This Is Good

• Scalability: Transitions from manual, per-user group assignments to efficient, plan-based operations.
• Efficiency: Supports batch operations for managing large user sets simultaneously.
• Data Integrity: Uses transaction-oriented update/reconcile flows to prevent state drift.
• Maintainability: Clearer domain modeling (package -> plan -> assignment) simplifies future enhancements.

🧪 Validation

• Backend: All service/handler unit tests passed in local verification.
• Frontend: Production build (npm run build) passed with no type errors.
• Manual Test: Verified bulk assignment and automatic reconciliation in the admin dashboard.

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