feat(frontend): add product detail view and navigation

- Create ProductView component with product details display
- Add ProductView.css with responsive styling
- Add product screen to App.jsx screen system
- Pass onNavigateToProduct callback from App to SearchView
- Update ProductResults onSelect to use callback instead of window.location

apps/frontend/src/views/SearchView.jsx

@@ -14,7 +14,7 @@ const suggestions = [
   { name: 'Omeprazol', icon: 'emergency_home', color: 'neutral-4' },
 ];
 
-function SearchView({ currentUser, onLoginRequest, initialQuery = '' }) {
+function SearchView({ currentUser, onLoginRequest, initialQuery = '', onNavigateToProduct }) {
   const [searchQuery, setSearchQuery] = useState(initialQuery);
   const [medicines, setMedicines] = useState([]);
   const [products, setProducts] = useState([]);
@@ -331,7 +331,11 @@ function SearchView({ currentUser, onLoginRequest, initialQuery = '' }) {
                 <ProductResults
                   products={products}
                   onSelect={(p) => {
-                    window.location.href = `/product/${p.source}/${p.id}`;
+                    if (onNavigateToProduct) {
+                      onNavigateToProduct(p.source, p.id);
+                    } else {
+                      window.location.href = `/product/${p.source}/${p.id}`;
+                    }
                   }}
                 />
               </div>