feat: add admin customer management

- Add admin customers API endpoints
- Add AdminCustomerService for customer operations
- Enhance customers.html template with management features
- Add customers.js Alpine component
- Add customer list schemas

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

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

models/schema/customer.py

@@ -248,8 +248,54 @@ class CustomerOrdersResponse(BaseModel):
 class CustomerStatisticsResponse(BaseModel):
     """Response for customer statistics."""
 
+    total: int = 0
+    active: int = 0
+    inactive: int = 0
+    with_orders: int = 0
+    total_spent: float = 0.0
+    total_orders: int = 0
+    avg_order_value: float = 0.0
+
+
+# ============================================================================
+# Admin Customer Management Response Schemas
+# ============================================================================
+
+
+class AdminCustomerItem(BaseModel):
+    """Admin customer list item with vendor info."""
+
+    id: int
+    vendor_id: int
+    email: str
+    first_name: str | None = None
+    last_name: str | None = None
+    phone: str | None = None
+    customer_number: str
+    marketing_consent: bool = False
+    preferred_language: str | None = None
+    last_order_date: datetime | None = None
     total_orders: int = 0
     total_spent: float = 0.0
-    average_order_value: float = 0.0
-    last_order_date: datetime | None = None
-    message: str | None = None
+    is_active: bool = True
+    created_at: datetime
+    updated_at: datetime
+    vendor_name: str | None = None
+    vendor_code: str | None = None
+
+    model_config = {"from_attributes": True}
+
+
+class CustomerListResponse(BaseModel):
+    """Admin paginated customer list with skip/limit."""
+
+    customers: list[AdminCustomerItem] = []
+    total: int = 0
+    skip: int = 0
+    limit: int = 20
+
+
+class CustomerDetailResponse(AdminCustomerItem):
+    """Detailed customer response for admin."""
+
+    pass