Add duplicate detection when adding items

- normalizeName() strips punctuation and normalizes whitespace/case
- findDuplicates() checks for matching normalized names
- Shows confirmation dialog if similar item exists

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

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

index.html

@@ -993,6 +993,22 @@
             return div.innerHTML;
         }
 
+        function normalizeName(name) {
+            return name
+                .toLowerCase()
+                .replace(/[^\w\s]/g, '')  // Remove punctuation
+                .replace(/\s+/g, ' ')      // Normalize whitespace
+                .trim();
+        }
+
+        function findDuplicates(name, excludeId = null) {
+            const normalized = normalizeName(name);
+            return inventory.filter(item => {
+                if (excludeId && item.id === excludeId) return false;
+                return normalizeName(item.name) === normalized;
+            });
+        }
+
         function updateStats() {
             const total = inventory.length;
             const inStock = inventory.filter(i => !i.outOfStock).length;
@@ -1225,9 +1241,20 @@
                 showToast('Please enter an item name');
                 return;
             }
-            
+
+            // Check for duplicates when adding new items
+            if (!editingId) {
+                const duplicates = findDuplicates(name);
+                if (duplicates.length > 0) {
+                    const dupNames = duplicates.map(d => d.name).join(', ');
+                    if (!confirm(`Similar item exists: "${dupNames}"\n\nAdd anyway?`)) {
+                        return;
+                    }
+                }
+            }
+
             showLoading();
-            
+
             try {
                 if (editingId) {
                     // Update existing