feat: multi-module improvements across merchant, store, i18n, and customer systems

- Fix platform-grouped merchant sidebar menu with core items at root level
- Add merchant store management (detail page, create store, team page)
- Fix store settings 500 error by removing dead stripe/API tab
- Move onboarding translations to module-owned locale files
- Fix onboarding banner i18n with server-side rendering + context inheritance
- Refactor login language selectors to use languageSelector() function (LANG-002)
- Move HTTPException handling to global exception handler in merchant routes (API-003)
- Add language selector to all login pages and portal headers
- Fix customer module: drop order stats from customer model, add to orders module
- Fix admin menu config visibility for super admin platform context
- Fix storefront auth and layout issues
- Add missing i18n translations for onboarding steps (en/fr/de/lb)

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

app/modules/orders/models/__init__.py

@@ -5,6 +5,7 @@ Orders module database models.
 This module contains the canonical implementations of order-related models.
 """
 
+from app.modules.orders.models.customer_order_stats import CustomerOrderStats
 from app.modules.orders.models.invoice import (
     Invoice,
     InvoiceStatus,
@@ -15,6 +16,7 @@ from app.modules.orders.models.order import Order, OrderItem
 from app.modules.orders.models.order_item_exception import OrderItemException
 
 __all__ = [
+    "CustomerOrderStats",
     "Order",
     "OrderItem",
     "OrderItemException",

app/modules/orders/models/customer_order_stats.py

@@ -0,0 +1,52 @@
+# app/modules/orders/models/customer_order_stats.py
+"""
+Customer order statistics model.
+
+Tracks per-customer order aggregates (total orders, total spent, etc.)
+owned by the orders module. This separates order stats from the
+customer profile data owned by the customers module.
+"""
+
+from sqlalchemy import Column, DateTime, ForeignKey, Index, Integer, UniqueConstraint
+from sqlalchemy.orm import relationship
+
+from app.core.database import Base
+from models.database.base import TimestampMixin
+
+
+class CustomerOrderStats(Base, TimestampMixin):
+    """Aggregated order statistics per customer per store."""
+
+    __tablename__ = "customer_order_stats"
+
+    id = Column(Integer, primary_key=True, index=True)
+    store_id = Column(
+        Integer, ForeignKey("stores.id"), nullable=False, index=True
+    )
+    customer_id = Column(
+        Integer, ForeignKey("customers.id"), nullable=False, index=True
+    )
+    total_orders = Column(Integer, nullable=False, default=0)
+    total_spent_cents = Column(Integer, nullable=False, default=0)
+    last_order_date = Column(DateTime(timezone=True), nullable=True)
+    first_order_date = Column(DateTime(timezone=True), nullable=True)
+
+    # Relationships
+    store = relationship("Store")
+    customer = relationship("Customer")
+
+    __table_args__ = (
+        UniqueConstraint(
+            "store_id", "customer_id", name="uq_customer_order_stats_store_customer"
+        ),
+        Index("idx_customer_order_stats_customer", "customer_id"),
+    )
+
+    def __repr__(self):
+        return (
+            f"<CustomerOrderStats("
+            f"store_id={self.store_id}, "
+            f"customer_id={self.customer_id}, "
+            f"total_orders={self.total_orders}, "
+            f"total_spent_cents={self.total_spent_cents})>"
+        )