Add autocomplete dropdowns for category and merchant in CategoryMappings

Improved UX for adding/editing category mappings:

**Backend Changes:**
- Added AvailableCategories list (distinct categories from existing mappings)
- Added AvailableMerchants list (all merchants from Merchants table)
- Updated LoadDataAsync() to populate both lists

**UI Changes:**
- Replaced plain text input with HTML5 datalist for Category field
- Replaced plain text input with HTML5 datalist for Merchant field
- Both fields support autocomplete while allowing new values
- Added "required" attribute to Category field for validation
- Added helper text to guide users
- Removed custom JavaScript dropdown logic (now using native datalist)

**Benefits:**
- Consistent category naming (autocomplete suggests existing categories)
- Consistent merchant naming (autocomplete suggests existing merchants)
- Better UX with native browser autocomplete behavior
- Still allows creating new categories/merchants on the fly
- Cleaner, simpler code without custom dropdown implementation

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude <noreply@anthropic.com>

MoneyMap/Pages/CategoryMappings.cshtml

@@ -157,20 +157,25 @@ else
                 <div class="modal-body">
                     <div class="mb-3">
                         <label for="addCategory" class="form-label">Category</label>
-                        <div class="position-relative">
+                        <input name="model.Category" id="addCategory" class="form-control" list="categoryList" placeholder="e.g., Online shopping" autocomplete="off" required />
-                            <input name="model.Category" id="addCategory" class="form-control" placeholder="e.g., Online shopping" autocomplete="off" />
+                        <datalist id="categoryList">
-                            <div id="addCategoryDropdown" class="dropdown-menu" style="width: 100%; max-height: 200px; overflow-y: auto;">
+                            @foreach (var category in Model.AvailableCategories)
-                                @foreach (var group in Model.CategoryGroups)
                             {
-                                    <a class="dropdown-item" href="#" data-category="@group.Category">@group.Category</a>
+                                <option value="@category">@category</option>
                             }
-                            </div>
+                        </datalist>
-                        </div>
+                        <div class="form-text">Select existing or type new category name</div>
                     </div>
 
                     <div class="mb-3">
                         <label for="addMerchant" class="form-label">Merchant Name (Optional)</label>
-                        <input name="model.Merchant" id="addMerchant" class="form-control" placeholder="e.g., Target" />
+                        <input name="model.Merchant" id="addMerchant" class="form-control" list="merchantList" placeholder="e.g., Target" autocomplete="off" />
+                        <datalist id="merchantList">
+                            @foreach (var merchant in Model.AvailableMerchants)
+                            {
+                                <option value="@merchant">@merchant</option>
+                            }
+                        </datalist>
                         <div class="form-text">Friendly name to assign to matching transactions (e.g., "Walmart" instead of "WAL-MART #1234")</div>
                     </div>
 
@@ -212,20 +217,13 @@ else
 
                     <div class="mb-3">
                         <label for="editCategory" class="form-label">Category</label>
-                        <div class="position-relative">
+                        <input name="model.Category" id="editCategory" class="form-control" list="categoryList" autocomplete="off" required />
-                            <input name="model.Category" id="editCategory" class="form-control" autocomplete="off" />
+                        <div class="form-text">Select existing or type new category name</div>
-                            <div id="editCategoryDropdown" class="dropdown-menu" style="width: 100%; max-height: 200px; overflow-y: auto;">
-                                @foreach (var group in Model.CategoryGroups)
-                                {
-                                    <a class="dropdown-item" href="#" data-category="@group.Category">@group.Category</a>
-                                }
-                            </div>
-                        </div>
                     </div>
 
                     <div class="mb-3">
                         <label for="editMerchant" class="form-label">Merchant Name (Optional)</label>
-                        <input name="model.Merchant" id="editMerchant" class="form-control" placeholder="e.g., Target" />
+                        <input name="model.Merchant" id="editMerchant" class="form-control" list="merchantList" placeholder="e.g., Target" autocomplete="off" />
                         <div class="form-text">Friendly name to assign to matching transactions (e.g., "Walmart" instead of "WAL-MART #1234")</div>
                     </div>
 
@@ -326,67 +324,7 @@ else
             }
         }
 
-        // Category dropdown functionality
-        function setupCategoryDropdown(inputId, dropdownId) {
-            const input = document.getElementById(inputId);
-            const dropdown = document.getElementById(dropdownId);
-
-            if (!input || !dropdown) return;
-
-            const dropdownItems = dropdown.querySelectorAll('.dropdown-item');
-
-            // Show dropdown on focus/click
-            input.addEventListener('focus', function() {
-                filterDropdown('');
-                dropdown.classList.add('show');
-            });
-
-            input.addEventListener('click', function() {
-                filterDropdown('');
-                dropdown.classList.add('show');
-            });
-
-            // Filter dropdown as user types
-            input.addEventListener('input', function() {
-                filterDropdown(this.value);
-                dropdown.classList.add('show');
-            });
-
-            // Select category from dropdown
-            dropdownItems.forEach(item => {
-                item.addEventListener('click', function(e) {
-                    e.preventDefault();
-                    e.stopPropagation();
-                    const category = this.getAttribute('data-category');
-                    input.value = category;
-                    dropdown.classList.remove('show');
-                });
-            });
-
-            // Close dropdown when clicking outside
-            document.addEventListener('click', function(e) {
-                if (!input.contains(e.target) && !dropdown.contains(e.target)) {
-                    dropdown.classList.remove('show');
-                }
-            });
-
-            // Filter dropdown items based on search text
-            function filterDropdown(searchText) {
-                const search = searchText.toLowerCase();
-                dropdownItems.forEach(item => {
-                    const category = item.getAttribute('data-category').toLowerCase();
-                    if (category.includes(search)) {
-                        item.style.display = '';
-                    } else {
-                        item.style.display = 'none';
-                    }
-                });
-            }
-        }
-
         document.addEventListener('DOMContentLoaded', function() {
-            setupCategoryDropdown('addCategory', 'addCategoryDropdown');
-            setupCategoryDropdown('editCategory', 'editCategoryDropdown');
 
             // Debug: Log form values before submission
             var addForm = document.querySelector('#addModal form');

MoneyMap/Pages/CategoryMappings.cshtml.cs

@@ -29,6 +29,8 @@ namespace MoneyMap.Pages
         public List<CategoryGroup> CategoryGroups { get; set; } = new();
         public int TotalMappings { get; set; }
         public int TotalCategories { get; set; }
+        public List<string> AvailableCategories { get; set; } = new();
+        public List<string> AvailableMerchants { get; set; } = new();
 
         [TempData]
         public string? SuccessMessage { get; set; }
@@ -251,6 +253,18 @@ namespace MoneyMap.Pages
 
             TotalMappings = mappings.Count;
             TotalCategories = CategoryGroups.Count;
+
+            // Get distinct categories for dropdown
+            AvailableCategories = CategoryGroups
+                .Select(g => g.Category)
+                .OrderBy(c => c)
+                .ToList();
+
+            // Get all merchants for dropdown
+            AvailableMerchants = await _db.Merchants
+                .OrderBy(m => m.Name)
+                .Select(m => m.Name)
+                .ToListAsync();
         }
 
         public class CategoryGroup