Implement quantity-based inventory tracking

- Replace checkboxes with quantity inputs for refill, vakuum, and otvoreno
- Display actual quantities in admin table instead of checkmarks
- Auto-parse existing data formats (e.g., "3 vakuum", "Da") to numbers
- Maintain backwards compatibility with existing data
- Update price auto-fill logic to work with quantity values
- Update tests to reflect new quantity inputs

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

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

__tests__/ui-features.test.ts

@@ -21,14 +21,17 @@ describe('UI Features Tests', () => {
     expect(tableContent).toContain('color.hex');
   });
 
-  it('should have checkboxes for boolean fields', () => {
+  it('should have number inputs for quantity fields', () => {
     const adminDashboardPath = join(process.cwd(), 'app', 'upadaj', 'dashboard', 'page.tsx');
     const adminContent = readFileSync(adminDashboardPath, 'utf-8');
     
-    // Check for checkbox inputs
-    expect(adminContent).toMatch(/type="checkbox"[\s\S]*?name="refill"/);
-    expect(adminContent).toMatch(/type="checkbox"[\s\S]*?name="vakum"/);
-    expect(adminContent).toMatch(/type="checkbox"[\s\S]*?name="otvoreno"/);
+    // Check for number inputs for quantities
+    expect(adminContent).toMatch(/type="number"[\s\S]*?name="refill"/);
+    expect(adminContent).toMatch(/type="number"[\s\S]*?name="vakum"/);
+    expect(adminContent).toMatch(/type="number"[\s\S]*?name="otvoreno"/);
+    expect(adminContent).toContain('Refill količina');
+    expect(adminContent).toContain('Vakuum količina');
+    expect(adminContent).toContain('Otvoreno količina');
   });
 
   it('should have number input for quantity', () => {