feat: implement localStorage for form parameter persistence

- Add saveFormValues() function to store all form parameters in localStorage
- Add restoreFormValues() function to retrieve form parameters from localStorage
- Modify DOMContentLoaded event to restore form values on page load
- Add calls to saveFormValues() in both form submission handlers
- Add event listeners to save form values whenever any input changes

This enhancement improves user experience by preserving form settings between visits.

app/templates/index.html

@@ -252,6 +252,45 @@
         let currentPage = 1;
         const pageSize = 10;
         
+        // Save form values to localStorage
+        function saveFormValues() {
+            const exerciseFormValues = {
+                minTable: document.getElementById('minTable').value,
+                maxTable: document.getElementById('maxTable').value,
+                numExercises: document.getElementById('numExercises').value,
+                multiplicationOnly: document.getElementById('multiplicationOnly').checked,
+                maxFirstOperand: document.getElementById('maxFirstOperand').value
+            };
+            
+            const operationFormValues = {
+                numOperationExercises: document.getElementById('numOperationExercises').value
+            };
+            
+            localStorage.setItem('exerciseFormValues', JSON.stringify(exerciseFormValues));
+            localStorage.setItem('operationFormValues', JSON.stringify(operationFormValues));
+        }
+        
+        // Restore form values from localStorage
+        function restoreFormValues() {
+            // Restore exercise form values
+            const savedExerciseValues = localStorage.getItem('exerciseFormValues');
+            if (savedExerciseValues) {
+                const exerciseValues = JSON.parse(savedExerciseValues);
+                document.getElementById('minTable').value = exerciseValues.minTable || 1;
+                document.getElementById('maxTable').value = exerciseValues.maxTable || 10;
+                document.getElementById('numExercises').value = exerciseValues.numExercises || 15;
+                document.getElementById('multiplicationOnly').checked = exerciseValues.multiplicationOnly || false;
+                document.getElementById('maxFirstOperand').value = exerciseValues.maxFirstOperand || 10;
+            }
+            
+            // Restore operation form values
+            const savedOperationValues = localStorage.getItem('operationFormValues');
+            if (savedOperationValues) {
+                const operationValues = JSON.parse(savedOperationValues);
+                document.getElementById('numOperationExercises').value = operationValues.numOperationExercises || 20;
+            }
+        }
+
         // Function to load and display existing PDFs with pagination (sorted from newest to oldest)
         async function loadPdfList(page = 1) {
             const refreshBtn = document.getElementById('refreshListBtn');
@@ -424,9 +463,18 @@
         
         // Load PDF list on page load
         document.addEventListener('DOMContentLoaded', function() {
+            restoreFormValues();
             loadPdfList(currentPage);
         });
         
+        // Add event listeners to save form values on change
+        document.getElementById('minTable').addEventListener('change', saveFormValues);
+        document.getElementById('maxTable').addEventListener('change', saveFormValues);
+        document.getElementById('numExercises').addEventListener('change', saveFormValues);
+        document.getElementById('multiplicationOnly').addEventListener('change', saveFormValues);
+        document.getElementById('maxFirstOperand').addEventListener('change', saveFormValues);
+        document.getElementById('numOperationExercises').addEventListener('change', saveFormValues);
+        
         // Event listener for select all button
         document.getElementById('selectAllBtn').addEventListener('click', function() {
             document.querySelectorAll('.file-checkbox').forEach(checkbox => {
@@ -523,6 +571,9 @@
         document.getElementById('exerciseForm').addEventListener('submit', async function(e) {
             e.preventDefault();
             
+            // Save form values to localStorage
+            saveFormValues();
+            
             const minTable = parseInt(document.getElementById('minTable').value);
             const maxTable = parseInt(document.getElementById('maxTable').value);
             const numExercises = parseInt(document.getElementById('numExercises').value);
@@ -606,8 +657,12 @@
         document.getElementById('operationExerciseForm').addEventListener('submit', async function(e) {
             e.preventDefault();
             
+            // Save form values to localStorage
+            saveFormValues();
+            
             const numExercises = parseInt(document.getElementById('numOperationExercises').value);
             
+            
             const generateBtn = document.getElementById('generateOperationBtn');
             const buttonText = document.getElementById('operationButtonText');
             const spinner = document.getElementById('operationSpinner');