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>

api/admin/handlers/offers-handlers.php

@@ -4,12 +4,6 @@ declare(strict_types=1);
 
 function handleGetList(PDO $pdo): void
 {
-    $search = trim($_GET['search'] ?? '');
-    $sort = $_GET['sort'] ?? 'created_at';
-    $order = strtoupper($_GET['order'] ?? 'DESC') === 'ASC' ? 'ASC' : 'DESC';
-    $page = max(1, (int) ($_GET['page'] ?? 1));
-    $perPage = min(500, max(1, (int) ($_GET['per_page'] ?? 500)));
-
     $sortMap = [
         'Date' => 'q.created_at',
         'CreatedAt' => 'q.created_at',
@@ -23,57 +17,37 @@ function handleGetList(PDO $pdo): void
         'Currency' => 'q.currency',
         'currency' => 'q.currency',
     ];
-    if (!isset($sortMap[$sort])) {
-        errorResponse('Neplatný parametr řazení', 400);
-    }
-    $sortCol = $sortMap[$sort];
 
+    $p = PaginationHelper::parseParams($sortMap);
     $where = 'WHERE 1=1';
     $params = [];
 
-    if ($search) {
-        $search = mb_substr($search, 0, 100);
+    if ($p['search']) {
         $where .= ' AND (q.quotation_number LIKE ? OR q.project_code LIKE ? OR c.name LIKE ?)';
-        $searchParam = "%{$search}%";
+        $searchParam = "%{$p['search']}%";
         $params = [$searchParam, $searchParam, $searchParam];
     }
 
-    // Celkovy pocet pro pagination
-    $countSql = "
-        SELECT COUNT(*)
-        FROM quotations q
-        LEFT JOIN customers c ON q.customer_id = c.id
-        $where
-    ";
-    $stmt = $pdo->prepare($countSql);
-    $stmt->execute($params);
-    $total = (int) $stmt->fetchColumn();
+    $from = "FROM quotations q LEFT JOIN customers c ON q.customer_id = c.id";
 
-    $offset = ($page - 1) * $perPage;
-
-    $sql = "
-        SELECT q.id, q.quotation_number, q.project_code, q.created_at, q.valid_until,
+    $result = PaginationHelper::paginate(
+        $pdo,
+        "SELECT COUNT(*) {$from} {$where}",
+        "SELECT q.id, q.quotation_number, q.project_code, q.created_at, q.valid_until,
                q.currency, q.language, q.apply_vat, q.vat_rate, q.exchange_rate,
                q.customer_id, q.order_id, q.status,
                c.name as customer_name,
                (SELECT COALESCE(SUM(CASE WHEN qi.is_included_in_total THEN qi.quantity * qi.unit_price ELSE 0 END), 0)
                 FROM quotation_items qi WHERE qi.quotation_id = q.id) as total
-        FROM quotations q
-        LEFT JOIN customers c ON q.customer_id = c.id
-        $where
-        ORDER BY $sortCol $order
-        LIMIT $perPage OFFSET $offset
-    ";
-
-    $stmt = $pdo->prepare($sql);
-    $stmt->execute($params);
-    $quotations = $stmt->fetchAll();
+        {$from} {$where}
+        ORDER BY {$p['sort']} {$p['order']}",
+        $params,
+        $p
+    );
 
     successResponse([
-        'quotations' => $quotations,
-        'total' => $total,
-        'page' => $page,
-        'per_page' => $perPage,
+        'quotations' => $result['items'],
+        'pagination' => $result['pagination'],
     ]);
 }