Refactor application to MVC architecture with Flask blueprints

Major architectural refactoring to improve code organization, maintainability, and scalability:

- Implement MVC pattern with clear separation of concerns
- Organize code into blueprints for different functional areas (main, tenant, admin, api)
- Create models layer to encapsulate all database operations
- Create services layer for business logic (auth, product, barcode)
- Implement application factory pattern for better testability
- Add environment-based configuration management
- Remove old monolithic app.py and consolidate routes

New structure:
- app/models/ - Database operations (Tenant, Product, ARField, Settings)
- app/services/ - Business logic (Auth, Product, Barcode services)
- app/blueprints/ - Controllers organized by function
- app/config.py - Environment configurations
- run.py - Application entry point

All routes remain backward compatible. No changes to API or templates functionality.

src/app/services/auth_service.py

@@ -0,0 +1,25 @@
+import base64
+from app.models import TenantModel
+
+class AuthService:
+    """Service for authentication logic"""
+
+    @staticmethod
+    def check_basic_auth(auth_header: str, tenant_id: str) -> bool:
+        """Validate Basic authentication credentials for a tenant"""
+        if not auth_header or not auth_header.startswith('Basic '):
+            return False
+
+        try:
+            # Decode the base64 credentials
+            credentials = base64.b64decode(auth_header[6:]).decode('utf-8')
+            username, password = credentials.split(':', 1)
+
+            # Get tenant credentials from database (without creating)
+            tenant = TenantModel.get_by_id(tenant_id)
+            if tenant and username == tenant['username'] and password == tenant['password']:
+                return True
+        except Exception:
+            pass
+
+        return False