feat: P2 strankovani - PaginationHelper, Pagination komponenta, integrace do 4 modulu

- PaginationHelper.php: parseParams() + paginate() - DRY backend pagination logika
- Pagination.jsx: frontend strankovaci komponenta (prev/next/cisla/info)
- CSS: .admin-pagination styly v admin.css
- Refaktor handleru: offers, orders, invoices, projects pouzivaji PaginationHelper
- Default 25 zaznamu na stranku (misto 500), max 500
- Frontend: page state + reset na search/filter zmenu
- useListData: pagination data v response

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

src/admin/pages/Invoices.jsx

@@ -11,6 +11,7 @@ import { formatCurrency, formatDate, czechPlural } from '../utils/formatters'
 import SortIcon from '../components/SortIcon'
 import useTableSort from '../hooks/useTableSort'
 import useListData from '../hooks/useListData'
+import Pagination from '../components/Pagination'
 
 const ReceivedInvoices = lazy(() => import('./ReceivedInvoices'))
 const API_BASE = '/api/admin'
@@ -65,6 +66,7 @@ export default function Invoices() {
   const [receivedUploadOpen, setReceivedUploadOpen] = useState(false)
   const { sort, order, handleSort, activeSort } = useTableSort('invoice_number')
   const [search, setSearch] = useState('')
+  const [page, setPage] = useState(1)
   const [statusFilter, setStatusFilter] = useState('')
 
   const now = new Date()
@@ -139,8 +141,8 @@ export default function Invoices() {
     setDraft(null)
   }
 
-  const { items: invoices, loading, refetch: fetchData } = useListData('invoices.php', {
-    dataKey: 'invoices', search, sort, order,
+  const { items: invoices, loading, pagination, refetch: fetchData } = useListData('invoices.php', {
+    dataKey: 'invoices', search, sort, order, page,
     extraParams: statusFilter ? { status: statusFilter } : {},
     errorMsg: 'Nepodařilo se načíst faktury'
   })
@@ -269,7 +271,7 @@ export default function Invoices() {
         <div>
           <h1 className="admin-page-title">Faktury</h1>
           <p className="admin-page-subtitle">
-            {invoices.length} {czechPlural(invoices.length, 'faktura', 'faktury', 'faktur')}
+            {pagination?.total ?? invoices.length} {czechPlural(pagination?.total ?? invoices.length, 'faktura', 'faktury', 'faktur')}
           </p>
         </div>
         {hasPermission('invoices.create') && (
@@ -430,7 +432,7 @@ export default function Invoices() {
             <button
               key={f.value}
               className={`offers-tab ${statusFilter === f.value ? 'active' : ''}`}
-              onClick={() => setStatusFilter(f.value)}
+              onClick={() => { setStatusFilter(f.value); setPage(1) }}
             >
               {f.label}
             </button>
@@ -450,7 +452,7 @@ export default function Invoices() {
             <input
               type="text"
               value={search}
-              onChange={(e) => setSearch(e.target.value)}
+              onChange={(e) => { setSearch(e.target.value); setPage(1) }}
               className="admin-form-input"
               placeholder="Hledat podle čísla faktury, zákazníka nebo IČ..."
             />
@@ -622,6 +624,7 @@ export default function Invoices() {
               </table>
             </div>
           )}
+          <Pagination pagination={pagination} onPageChange={setPage} />
         </div>
       </motion.div>