feat: add invoicing system and subscription tier enforcement

Phase 1 OMS implementation:

Invoicing:
- Add Invoice and VendorInvoiceSettings database models
- Full EU VAT support (27 countries, OSS, B2B reverse charge)
- Invoice PDF generation with WeasyPrint + Jinja2 templates
- Vendor invoice API endpoints for settings, creation, PDF download

Subscription Tiers:
- Add VendorSubscription model with 4 tiers (Essential/Professional/Business/Enterprise)
- Tier limit enforcement for orders, products, team members
- Feature gating based on subscription tier
- Automatic trial subscription creation for new vendors
- Integrate limit checks into order creation (direct and Letzshop sync)

Marketing:
- Update pricing documentation with 4-tier structure
- Revise back-office positioning strategy
- Update homepage with Veeqo-inspired Letzshop-focused messaging

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

app/services/order_service.py

@@ -31,6 +31,10 @@ from app.exceptions import (
     ValidationException,
 )
 from app.services.order_item_exception_service import order_item_exception_service
+from app.services.subscription_service import (
+    subscription_service,
+    TierLimitExceededException,
+)
 from app.utils.money import Money, cents_to_euros, euros_to_cents
 from models.database.customer import Customer
 from models.database.marketplace_product import MarketplaceProduct
@@ -271,7 +275,11 @@ class OrderService:
         Raises:
             ValidationException: If order data is invalid
             InsufficientInventoryException: If not enough inventory
+            TierLimitExceededException: If vendor has reached order limit
         """
+        # Check tier limit before creating order
+        subscription_service.check_order_limit(db, vendor_id)
+
         try:
             # Get or create customer
             if order_data.customer_id:
@@ -428,6 +436,9 @@ class OrderService:
             db.flush()
             db.refresh(order)
 
+            # Increment order count for subscription tracking
+            subscription_service.increment_order_count(db, vendor_id)
+
             logger.info(
                 f"Order {order.order_number} created for vendor {vendor_id}, "
                 f"total: EUR {cents_to_euros(total_amount_cents):.2f}"
@@ -439,6 +450,7 @@ class OrderService:
             ValidationException,
             InsufficientInventoryException,
             CustomerNotFoundException,
+            TierLimitExceededException,
         ):
             raise
         except Exception as e:
@@ -450,6 +462,7 @@ class OrderService:
         db: Session,
         vendor_id: int,
         shipment_data: dict[str, Any],
+        skip_limit_check: bool = False,
     ) -> Order:
         """
         Create an order from Letzshop shipment data.
@@ -462,13 +475,27 @@ class OrderService:
             db: Database session
             vendor_id: Vendor ID
             shipment_data: Raw shipment data from Letzshop API
+            skip_limit_check: If True, skip tier limit check (for batch imports
+                              that check limit upfront)
 
         Returns:
             Created Order object
 
         Raises:
             ValidationException: If product not found by GTIN
+            TierLimitExceededException: If vendor has reached order limit
         """
+        # Check tier limit before creating order (unless skipped for batch ops)
+        if not skip_limit_check:
+            can_create, message = subscription_service.can_create_order(db, vendor_id)
+            if not can_create:
+                raise TierLimitExceededException(
+                    message=message or "Order limit exceeded",
+                    limit_type="orders",
+                    current=0,  # Will be filled by caller if needed
+                    limit=0,
+                )
+
         order_data = shipment_data.get("order", {})
 
         # Generate order number using Letzshop order number
@@ -777,6 +804,9 @@ class OrderService:
                 f"order {order.order_number}"
             )
 
+        # Increment order count for subscription tracking
+        subscription_service.increment_order_count(db, vendor_id)
+
         logger.info(
             f"Letzshop order {order.order_number} created for vendor {vendor_id}, "
             f"status: {status}, items: {len(inventory_units)}"