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/models/base.py

@@ -0,0 +1,111 @@
+import sqlite3
+from contextlib import contextmanager
+from flask import current_app
+
+@contextmanager
+def get_db():
+    """Context manager for database connections"""
+    db_path = current_app.config['DATABASE_PATH']
+    conn = sqlite3.connect(db_path)
+    conn.row_factory = sqlite3.Row
+    try:
+        yield conn
+    finally:
+        conn.close()
+
+def init_database():
+    """Initialize the database with required tables"""
+    import os
+    db_path = current_app.config['DATABASE_PATH']
+    os.makedirs(os.path.dirname(db_path), exist_ok=True)
+
+    with get_db() as conn:
+        cursor = conn.cursor()
+
+        # Create tenants table
+        cursor.execute('''
+            CREATE TABLE IF NOT EXISTS tenants (
+                id TEXT PRIMARY KEY,
+                name TEXT NOT NULL,
+                username TEXT,
+                password TEXT,
+                barcode_type TEXT DEFAULT 'qr',
+                created_at TIMESTAMP DEFAULT CURRENT_TIMESTAMP,
+                updated_at TIMESTAMP DEFAULT CURRENT_TIMESTAMP
+            )
+        ''')
+
+        # Create products table with tenant_id
+        cursor.execute('''
+            CREATE TABLE IF NOT EXISTS products (
+                id TEXT,
+                tenant_id TEXT NOT NULL,
+                name TEXT NOT NULL,
+                price TEXT,
+                inventory INTEGER,
+                image_data BLOB,
+                image_mime_type TEXT,
+                created_at TIMESTAMP DEFAULT CURRENT_TIMESTAMP,
+                updated_at TIMESTAMP DEFAULT CURRENT_TIMESTAMP,
+                PRIMARY KEY (id, tenant_id),
+                FOREIGN KEY (tenant_id) REFERENCES tenants(id) ON DELETE CASCADE
+            )
+        ''')
+
+        # Create product_fields table with tenant_id
+        cursor.execute('''
+            CREATE TABLE IF NOT EXISTS product_fields (
+                product_id TEXT,
+                tenant_id TEXT,
+                field_name TEXT,
+                label TEXT,
+                value TEXT,
+                editable TEXT,
+                field_type TEXT,
+                FOREIGN KEY (product_id, tenant_id) REFERENCES products(id, tenant_id) ON DELETE CASCADE,
+                PRIMARY KEY (product_id, tenant_id, field_name)
+            )
+        ''')
+
+        # Create custom_ar_fields table for tenant-specific AR field definitions
+        cursor.execute('''
+            CREATE TABLE IF NOT EXISTS custom_ar_fields (
+                id INTEGER PRIMARY KEY AUTOINCREMENT,
+                tenant_id TEXT NOT NULL,
+                field_name TEXT NOT NULL,
+                label TEXT NOT NULL,
+                field_type TEXT NOT NULL,
+                editable TEXT DEFAULT 'true',
+                display_order INTEGER DEFAULT 0,
+                created_at TIMESTAMP DEFAULT CURRENT_TIMESTAMP,
+                updated_at TIMESTAMP DEFAULT CURRENT_TIMESTAMP,
+                FOREIGN KEY (tenant_id) REFERENCES tenants(id) ON DELETE CASCADE,
+                UNIQUE(tenant_id, field_name)
+            )
+        ''')
+
+        # Create product_images table for storing multiple images per product
+        cursor.execute('''
+            CREATE TABLE IF NOT EXISTS product_images (
+                id INTEGER PRIMARY KEY AUTOINCREMENT,
+                product_id TEXT NOT NULL,
+                tenant_id TEXT NOT NULL,
+                field_name TEXT NOT NULL,
+                image_data BLOB NOT NULL,
+                image_mime_type TEXT NOT NULL,
+                created_at TIMESTAMP DEFAULT CURRENT_TIMESTAMP,
+                FOREIGN KEY (product_id, tenant_id) REFERENCES products(id, tenant_id) ON DELETE CASCADE,
+                UNIQUE(product_id, tenant_id, field_name)
+            )
+        ''')
+
+        # Create settings table
+        cursor.execute('''
+            CREATE TABLE IF NOT EXISTS settings (
+                key TEXT PRIMARY KEY,
+                value TEXT NOT NULL,
+                updated_at TIMESTAMP DEFAULT CURRENT_TIMESTAMP
+            )
+        ''')
+
+        conn.commit()