Epic 5 Complete: Billing, Subscriptions, and Admin Features

Resolve all 5 deferred items from Epic 5 adversarial code review:
- Migration 124: Add CASCADE to subscriptionstatus enum drop (prevent orphaned references)
- Stripe rate limiting: In-memory per-user limiter (20 calls/60s) on verify-checkout-session
- Subscription request cooldown: 24h cooldown before resubmitting rejected requests
- Token reset date: Initialize on first subscription activation
- Checkout URL validation: Confirmed HTTPS-only (Stripe always returns HTTPS)

Implement Story 5.4 (Usage Tracking & Rate Limit Enforcement):
- Page quota pre-check at HTTP upload layer
- Extend UserRead schema with token quota fields
- Frontend 402 error handling in document upload
- Quota indicator in dashboard sidebar

Story 5.5 (Admin Seed & Approval Flow):
- Seed admin user migration with default credentials warning
- Subscription approval/rejection routes with admin guard
- 24h rejection cooldown enforcement

Story 5.6 (Admin-Only Model Config):
- Global model config visible across all search spaces
- Per-search-space model configs with user access control
- Superuser CRUD for global configs

Additional fixes from code review:
- PageLimitService: PAST_DUE subscriptions enforce free-tier limits
- TokenQuotaService: PAST_DUE subscriptions enforce free-tier limits
- Config routes: Fixed user_id.is_(None) filter on mutation endpoints
- Stripe webhook: Added guard against silent plan downgrade on unrecognized price_id

All changes formatted with Ruff (Python) and Biome (TypeScript).

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

surfsense_backend/app/routes/__init__.py

@@ -48,6 +48,7 @@ from .sandbox_routes import router as sandbox_router
 from .search_source_connectors_routes import router as search_source_connectors_router
 from .search_spaces_routes import router as search_spaces_router
 from .slack_add_connector_route import router as slack_add_connector_router
+from .admin_routes import router as admin_router
 from .stripe_routes import router as stripe_router
 from .surfsense_docs_routes import router as surfsense_docs_router
 from .teams_add_connector_route import router as teams_add_connector_router
@@ -100,6 +101,7 @@ router.include_router(notifications_router)  # Notifications with Zero sync
 router.include_router(composio_router)  # Composio OAuth and toolkit management
 router.include_router(public_chat_router)  # Public chat sharing and cloning
 router.include_router(incentive_tasks_router)  # Incentive tasks for earning free pages
+router.include_router(admin_router)  # Superuser admin operations
 router.include_router(stripe_router)  # Stripe checkout for additional page packs
 router.include_router(youtube_router)  # YouTube playlist resolution
 router.include_router(prompts_router)