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/__init__.py

@@ -0,0 +1,49 @@
+import os
+from flask import Flask, redirect
+from werkzeug.routing import BaseConverter
+
+def create_app(config_name='development'):
+    """Application factory pattern"""
+    app = Flask(__name__)
+
+    # Load configuration
+    from app.config import config
+    app.config.from_object(config[config_name])
+
+    # Ensure data folder exists
+    os.makedirs(app.config['DATA_FOLDER'], exist_ok=True)
+
+    # Custom converter for tenant IDs
+    class TenantConverter(BaseConverter):
+        regex = '[a-zA-Z0-9_-]+'
+
+        def to_python(self, value):
+            # Convert to lowercase when parsing from URL
+            return value.lower()
+
+        def to_url(self, value):
+            # Convert to lowercase when generating URLs
+            return value.lower()
+
+    app.url_map.converters['tenant'] = TenantConverter
+
+    # Initialize database
+    with app.app_context():
+        from app.models.base import init_database
+        init_database()
+
+    # Register blueprints
+    from app.blueprints import main_bp, tenant_bp, admin_bp, api_bp
+
+    app.register_blueprint(main_bp)
+    app.register_blueprint(tenant_bp)
+    app.register_blueprint(admin_bp)
+    app.register_blueprint(api_bp)
+
+    # Catch-all route for admin without tenant - redirect to home
+    @app.route('/admin/')
+    @app.route('/admin/<path:path>')
+    def redirect_admin_to_home(path=None):
+        return redirect('/')
+
+    return app