Add import labels functionality to labels module

- Created import_labels.py with CSV and Excel file processing
- Implemented validation for order rows and date format handling
- Added import-labels route with preview and save functionality
- Created import_labels.html template with new app UI styling
- Added import card to labels module index
- Added openpyxl to requirements.txt for Excel support

app/templates/modules/labels/index.html

@@ -30,6 +30,22 @@
             </div>
         </div>
 
+        <!-- Import Labels Card -->
+        <div class="col-md-6 col-lg-4 mb-4">
+            <div class="card shadow-sm h-100 module-launcher">
+                <div class="card-body text-center">
+                    <div class="launcher-icon mb-3">
+                        <i class="fas fa-file-import text-info"></i>
+                    </div>
+                    <h5 class="card-title">Import Labels Data</h5>
+                    <p class="card-text text-muted">Upload CSV or Excel files with order data for label printing.</p>
+                    <a href="{{ url_for('labels.import_labels') }}" class="btn btn-info btn-sm">
+                        <i class="fas fa-arrow-right"></i> Import Data
+                    </a>
+                </div>
+            </div>
+        </div>
+
         <!-- Print Lost Labels Card -->
         <div class="col-md-6 col-lg-4 mb-4">
             <div class="card shadow-sm h-100 module-launcher">