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/documents_routes.py

@@ -73,6 +73,24 @@ async def create_documents(
             "You don't have permission to create documents in this search space",
         )
 
+        # Page quota pre-check for connector documents
+        from app.services.page_limit_service import (
+            PageLimitExceededError,
+            PageLimitService,
+        )
+
+        estimated_pages = len(request.content)  # 1 page per document/URL
+        try:
+            page_service = PageLimitService(session)
+            await page_service.check_page_limit(str(user.id), estimated_pages)
+        except PageLimitExceededError as e:
+            raise HTTPException(
+                status_code=402,
+                detail=f"Page quota exceeded ({e.pages_used}/{e.pages_limit}). "
+                f"This request requires ~{estimated_pages} pages. "
+                f"Upgrade your plan for more pages.",
+            ) from e
+
         if request.document_type == DocumentType.EXTENSION:
             from app.tasks.celery_tasks.document_tasks import (
                 process_extension_document_task,
@@ -169,6 +187,30 @@ async def create_documents_file_upload(
                     f"exceeds the {MAX_FILE_SIZE_BYTES // (1024 * 1024)} MB per-file limit.",
                 )
 
+        # Page quota pre-check
+        from app.services.page_limit_service import (
+            PageLimitExceededError,
+            PageLimitService,
+        )
+
+        total_estimated_pages = sum(
+            PageLimitService.estimate_pages_from_metadata(
+                file.filename or "", file.size or 0
+            )
+            for file in files
+        )
+
+        try:
+            page_service = PageLimitService(session)
+            await page_service.check_page_limit(str(user.id), total_estimated_pages)
+        except PageLimitExceededError as e:
+            raise HTTPException(
+                status_code=402,
+                detail=f"Page quota exceeded ({e.pages_used}/{e.pages_limit}). "
+                f"This upload requires ~{total_estimated_pages} pages. "
+                f"Upgrade your plan for more pages.",
+            ) from e
+
         # ===== Read all files concurrently to avoid blocking the event loop =====
         async def _read_and_save(file: UploadFile) -> tuple[str, str, int]:
             """Read upload content and write to temp file off the event loop."""