feat: Migrate label printing module from legacy app

- Created labels module with complete structure in app/modules/labels/
- Implemented print_module.py with database functions:
  * get_unprinted_orders_data() - Retrieve unprinted orders from database
  * get_printed_orders_data() - Retrieve printed orders from database
  * update_order_printed_status() - Mark orders as printed
  * search_orders_by_cp_code() - Search orders by production code
- Created routes.py with Flask Blueprint and API endpoints:
  * GET /labels/ - Module home page with feature launchers
  * GET /labels/print-module - Main label printing interface
  * GET /labels/print-lost-labels - Lost label reprinting interface
  * GET /labels/api/unprinted-orders - API for unprinted orders
  * GET /labels/api/printed-orders - API for printed orders
  * POST /labels/api/search-orders - Search orders API
  * POST /labels/api/update-printed-status/<id> - Update status API
- Migrated HTML templates from legacy app with theme support:
  * print_module.html - Thermal label printing with QZ Tray integration
  * print_lost_labels.html - Lost label search and reprint interface
  * Added comprehensive CSS variables for dark/light mode theming
  * Preserved all original JavaScript functionality for printing
- Created index.html module home page with feature launchers
- Registered labels blueprint in app/__init__.py with /labels prefix
- Added 'Label Printing' module card to dashboard with print icon

All functionality preserved from original implementation:
- QZ Tray thermal printer integration
- JsBarcode barcode generation (horizontal + vertical)
- PDF export fallback
- Session-based authentication for all routes
- Database integration with proper error handling

app/modules/labels/routes.py

@@ -0,0 +1,128 @@
+"""
+Labels Module Routes
+Handles label printing pages and API endpoints
+"""
+from flask import Blueprint, render_template, session, redirect, url_for, jsonify, request
+import logging
+
+from .print_module import (
+    get_unprinted_orders_data, 
+    get_printed_orders_data,
+    update_order_printed_status,
+    search_orders_by_cp_code
+)
+
+logger = logging.getLogger(__name__)
+
+labels_bp = Blueprint('labels', __name__, url_prefix='/labels')
+
+
+@labels_bp.route('/', methods=['GET'])
+def labels_index():
+    """Labels module home page"""
+    if 'user_id' not in session:
+        return redirect(url_for('main.login'))
+    
+    return render_template('modules/labels/index.html')
+
+
+@labels_bp.route('/print-module', methods=['GET'])
+def print_module():
+    """Label printing interface with thermal printer support"""
+    if 'user_id' not in session:
+        return redirect(url_for('main.login'))
+    
+    return render_template('modules/labels/print_module.html')
+
+
+@labels_bp.route('/print-lost-labels', methods=['GET'])
+def print_lost_labels():
+    """Print lost/missing labels interface"""
+    if 'user_id' not in session:
+        return redirect(url_for('main.login'))
+    
+    return render_template('modules/labels/print_lost_labels.html')
+
+
+# ============================================================================
+# API Endpoints for Labels Module
+# ============================================================================
+
+@labels_bp.route('/api/unprinted-orders', methods=['GET'], endpoint='api_unprinted_orders')
+def api_unprinted_orders():
+    """Get all unprinted orders for label printing"""
+    if 'user_id' not in session:
+        return jsonify({'success': False, 'error': 'Unauthorized'}), 401
+    
+    try:
+        limit = request.args.get('limit', 100, type=int)
+        if limit > 500:
+            limit = 500
+        if limit < 1:
+            limit = 1
+        
+        orders = get_unprinted_orders_data(limit)
+        return jsonify({'success': True, 'orders': orders, 'count': len(orders)}), 200
+    except Exception as e:
+        logger.error(f"Error getting unprinted orders: {e}")
+        return jsonify({'success': False, 'error': str(e)}), 500
+
+
+@labels_bp.route('/api/printed-orders', methods=['GET'], endpoint='api_printed_orders')
+def api_printed_orders():
+    """Get all printed orders"""
+    if 'user_id' not in session:
+        return jsonify({'success': False, 'error': 'Unauthorized'}), 401
+    
+    try:
+        limit = request.args.get('limit', 100, type=int)
+        if limit > 500:
+            limit = 500
+        if limit < 1:
+            limit = 1
+        
+        orders = get_printed_orders_data(limit)
+        return jsonify({'success': True, 'orders': orders, 'count': len(orders)}), 200
+    except Exception as e:
+        logger.error(f"Error getting printed orders: {e}")
+        return jsonify({'success': False, 'error': str(e)}), 500
+
+
+@labels_bp.route('/api/search-orders', methods=['POST'], endpoint='api_search_orders')
+def api_search_orders():
+    """Search for orders by CP code"""
+    if 'user_id' not in session:
+        return jsonify({'success': False, 'error': 'Unauthorized'}), 401
+    
+    try:
+        data = request.get_json()
+        cp_code = data.get('cp_code', '').strip()
+        
+        if not cp_code or len(cp_code) < 1:
+            return jsonify({'success': False, 'error': 'CP code is required'}), 400
+        
+        results = search_orders_by_cp_code(cp_code)
+        return jsonify({'success': True, 'orders': results, 'count': len(results)}), 200
+    except Exception as e:
+        logger.error(f"Error searching orders: {e}")
+        return jsonify({'success': False, 'error': str(e)}), 500
+
+
+@labels_bp.route('/api/update-printed-status/<int:order_id>', methods=['POST'], endpoint='api_update_printed_status')
+def api_update_printed_status(order_id):
+    """Mark an order as printed"""
+    if 'user_id' not in session:
+        return jsonify({'success': False, 'error': 'Unauthorized'}), 401
+    
+    try:
+        data = request.get_json() or {}
+        printed = data.get('printed', True)
+        
+        success = update_order_printed_status(order_id, printed)
+        if success:
+            return jsonify({'success': True, 'message': 'Order status updated'}), 200
+        else:
+            return jsonify({'success': False, 'error': 'Failed to update order'}), 500
+    except Exception as e:
+        logger.error(f"Error updating order status: {e}")
+        return jsonify({'success': False, 'error': str(e)}), 500