Add admin sorting options and prevent zero quantity filament creation

- Add sorting dropdown with Serbian labels (alphabetical, date-based, quantity)
- Fix Safari dropdown styling with custom-select class
- Add validation to prevent adding filaments with 0 quantity
- Improve sort dropdown layout and error handling

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

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

app/upadaj/dashboard/page.tsx

@@ -158,7 +158,21 @@ export default function AdminDashboard() {
       if (aVal === null || aVal === undefined) aVal = '';
       if (bVal === null || bVal === undefined) bVal = '';
       
-      // Convert to strings for comparison
+      // Handle date fields
+      if (sortField === 'created_at' || sortField === 'updated_at') {
+        const aDate = new Date(String(aVal));
+        const bDate = new Date(String(bVal));
+        return sortOrder === 'asc' ? aDate.getTime() - bDate.getTime() : bDate.getTime() - aDate.getTime();
+      }
+      
+      // Handle numeric fields
+      if (sortField === 'kolicina' || sortField === 'refill' || sortField === 'spulna') {
+        const aNum = Number(aVal) || 0;
+        const bNum = Number(bVal) || 0;
+        return sortOrder === 'asc' ? aNum - bNum : bNum - aNum;
+      }
+      
+      // String comparison for other fields
       aVal = String(aVal).toLowerCase();
       bVal = String(bVal).toLowerCase();
       
@@ -355,19 +369,54 @@ export default function AdminDashboard() {
           </div>
         )}
 
-        {/* Search Bar */}
+        {/* Search Bar and Sorting */}
         <div className="mb-6">
-          <div className="relative">
+          <div className="grid grid-cols-1 sm:grid-cols-2 gap-4">
-            <input
+            {/* Search Input */}
-              type="text"
+            <div className="relative">
-              placeholder="Pretraži po tipu, finishu, boji ili ceni..."
+              <input
-              value={searchTerm}
+                type="text"
-              onChange={(e) => setSearchTerm(e.target.value)}
+                placeholder="Pretraži po tipu, finishu, boji ili ceni..."
-              className="w-full px-4 py-2 pl-10 pr-4 text-gray-700 dark:text-gray-300 bg-white dark:bg-gray-800 border border-gray-300 dark:border-gray-600 rounded-lg focus:outline-none focus:border-blue-500"
+                value={searchTerm}
-            />
+                onChange={(e) => setSearchTerm(e.target.value)}
-            <svg className="absolute left-3 top-2.5 h-5 w-5 text-gray-400" fill="none" stroke="currentColor" viewBox="0 0 24 24">
+                className="w-full px-4 py-2 pl-10 pr-4 text-gray-700 dark:text-gray-300 bg-white dark:bg-gray-800 border border-gray-300 dark:border-gray-600 rounded-lg focus:outline-none focus:border-blue-500"
-              <path strokeLinecap="round" strokeLinejoin="round" strokeWidth={2} d="M21 21l-6-6m2-5a7 7 0 11-14 0 7 7 0 0114 0z" />
+              />
-            </svg>
+              <svg className="absolute left-3 top-2.5 h-5 w-5 text-gray-400" fill="none" stroke="currentColor" viewBox="0 0 24 24">
+                <path strokeLinecap="round" strokeLinejoin="round" strokeWidth={2} d="M21 21l-6-6m2-5a7 7 0 11-14 0 7 7 0 0114 0z" />
+              </svg>
+            </div>
+            
+            {/* Sort Dropdown */}
+            <div>
+              <select
+                value={`${sortField || 'boja'}-${sortOrder || 'asc'}`}
+                onChange={(e) => {
+                  try {
+                    const [field, order] = e.target.value.split('-');
+                    if (field && order) {
+                      setSortField(field);
+                      setSortOrder(order as 'asc' | 'desc');
+                    }
+                  } catch (error) {
+                    console.error('Sort change error:', error);
+                  }
+                }}
+                className="custom-select w-full px-3 py-2 text-gray-700 dark:text-gray-300 bg-white dark:bg-gray-800 border border-gray-300 dark:border-gray-600 rounded-md focus:outline-none focus:border-blue-500"
+              >
+                <option value="boja-asc">Sortiraj po: Boja (A-Z)</option>
+                <option value="boja-desc">Sortiraj po: Boja (Z-A)</option>
+                <option value="tip-asc">Sortiraj po: Tip (A-Z)</option>
+                <option value="tip-desc">Sortiraj po: Tip (Z-A)</option>
+                <option value="finish-asc">Sortiraj po: Finish (A-Z)</option>
+                <option value="finish-desc">Sortiraj po: Finish (Z-A)</option>
+                <option value="created_at-desc">Sortiraj po: Poslednje dodano</option>
+                <option value="created_at-asc">Sortiraj po: Prvo dodano</option>
+                <option value="updated_at-desc">Sortiraj po: Poslednje ažurirano</option>
+                <option value="updated_at-asc">Sortiraj po: Prvo ažurirano</option>
+                <option value="kolicina-desc">Sortiraj po: Količina (visoka-niska)</option>
+                <option value="kolicina-asc">Sortiraj po: Količina (niska-visoka)</option>
+              </select>
+            </div>
           </div>
         </div>
 
@@ -637,6 +686,12 @@ function FilamentForm({
     // Calculate total quantity
     const totalQuantity = formData.refill + formData.spulna;
     
+    // Prevent adding filaments with 0 quantity
+    if (totalQuantity === 0) {
+      alert('Količina mora biti veća od 0. Dodajte refill ili spulna.');
+      return;
+    }
+    
     // Use the prices from the form (which can be edited)
     const refillPrice = formData.cena_refill;
     const spoolPrice = formData.cena_spulna;