New router: routers/subscription.py
Endpoints:
- GET /api/subscription/me - Own subscription info (tier, trial, grants)
- GET /api/subscription/usage - Feature usage with limits
- GET /api/subscription/limits - All feature limits for current tier
Features:
- Shows effective tier (considers access_grants)
- Lists active access grants (from coupons, trials)
- Per-feature usage tracking
- Email verification status
Uses new middleware: get_effective_tier(), check_feature_access()
Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>
