Add bulk price editing features and fix quantity update price preservation

- Fix FilamentForm to preserve prices when updating quantities
  - Add isInitialLoad flag to prevent price override on form load
  - Only update prices when color is actively changed, not on initial render

- Add bulk filament price editor to dashboard
  - Filter by material and finish
  - Set refill and/or spool prices for multiple filaments
  - Preview changes before applying
  - Update all filtered filaments at once

- Add bulk color price editor to colors page
  - Edit prices for all colors in one interface
  - Global price application with search filtering
  - Individual price editing with change tracking

- Add auto-kill script for dev server
  - Kill existing processes on ports 3000/3001 before starting
  - Prevent "port already in use" errors
  - Clean start every time npm run dev is executed

app/upadaj/dashboard/page.tsx

@@ -6,6 +6,7 @@ import { filamentService, colorService } from '@/src/services/api';
 import { Filament } from '@/src/types/filament';
 import { trackEvent } from '@/src/components/MatomoAnalytics';
 import { SaleManager } from '@/src/components/SaleManager';
+import { BulkFilamentPriceEditor } from '@/src/components/BulkFilamentPriceEditor';
 // Removed unused imports for Bambu Lab color categorization
 import '@/src/styles/select.css';
 
@@ -391,11 +392,15 @@ export default function AdminDashboard() {
                       Obriši izabrane ({selectedFilaments.size})
                     </button>
                   )}
-                  <SaleManager 
+                  <SaleManager
                     filaments={filaments}
                     selectedFilaments={selectedFilaments}
                     onSaleUpdate={fetchFilaments}
                   />
+                  <BulkFilamentPriceEditor
+                    filaments={filaments}
+                    onUpdate={fetchFilaments}
+                  />
                   <button
                     onClick={() => router.push('/upadaj/colors')}
                     className="flex-1 sm:flex-initial px-3 sm:px-4 py-2 bg-purple-500 text-white rounded hover:bg-purple-600 text-sm sm:text-base"
@@ -713,23 +718,26 @@ function FilamentForm({
     cena_spulna: 0,
   });
 
+  // Track if this is the initial load to prevent price override
+  const [isInitialLoad, setIsInitialLoad] = useState(true);
+
   // Update form when filament prop changes
   useEffect(() => {
     // Extract prices from the cena field if it exists (format: "3499/3999" or just "3499")
     let refillPrice = 0;
     let spulnaPrice = 0;
-    
+
     if (filament.cena) {
       const prices = filament.cena.split('/');
       refillPrice = parseInt(prices[0]) || 0;
       spulnaPrice = prices.length > 1 ? parseInt(prices[1]) || 0 : parseInt(prices[0]) || 0;
     }
-    
+
     // Get default prices from color
     const colorData = availableColors.find(c => c.name === filament.boja);
     if (!refillPrice && colorData?.cena_refill) refillPrice = colorData.cena_refill;
     if (!spulnaPrice && colorData?.cena_spulna) spulnaPrice = colorData.cena_spulna;
-    
+
     setFormData({
       tip: filament.tip || (filament.id ? '' : 'PLA'), // Default to PLA for new filaments
       finish: filament.finish || (filament.id ? '' : 'Basic'), // Default to Basic for new filaments
@@ -742,10 +750,19 @@ function FilamentForm({
       cena_refill: refillPrice || 3499,
       cena_spulna: spulnaPrice || 3999,
     });
+
+    // Reset initial load flag when filament changes
+    setIsInitialLoad(true);
   }, [filament]);
 
-  // Update prices when color selection changes
+  // Update prices when color selection changes (but not on initial load)
   useEffect(() => {
+    // Skip price update on initial load to preserve existing filament prices
+    if (isInitialLoad) {
+      setIsInitialLoad(false);
+      return;
+    }
+
     if (formData.boja && availableColors.length > 0) {
       const colorData = availableColors.find(c => c.name === formData.boja);
       if (colorData) {