feat: P4 backend kvalita - SELECT * fix, overdue konsolidace, Validator

- SELECT * nahrazen explicitnimi sloupci ve 22 PHP souborech (69+ vyskytu)
- users-handlers.php: password_hash explicitne vyloucen z dotazu
- Overdue detekce presunuta do invoices.php routeru (1x pred dispatch misto 3x v handlerech)
- Validator.php: validacni helper s pravidly required, string, int, email, in, numeric
- PaginationHelper: PHPStan typy opraveny

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

api/admin/handlers/offers-templates-handlers.php

@@ -4,7 +4,10 @@ declare(strict_types=1);
 
 function handleGetItemTemplates(PDO $pdo): void
 {
-    $stmt = $pdo->query('SELECT * FROM item_templates ORDER BY category, name');
+    $stmt = $pdo->query(
+        'SELECT id, name, description, default_price, category
+        FROM item_templates ORDER BY category, name'
+    );
     successResponse(['templates' => $stmt->fetchAll()]);
 }
 
@@ -100,13 +103,17 @@ function handleDeleteItemTemplate(PDO $pdo, int $id): void
 
 function handleGetScopeTemplates(PDO $pdo): void
 {
-    $stmt = $pdo->query('SELECT * FROM scope_templates ORDER BY name');
+    $stmt = $pdo->query(
+        'SELECT id, name, title, description FROM scope_templates ORDER BY name'
+    );
     successResponse(['templates' => $stmt->fetchAll()]);
 }
 
 function handleGetScopeDetail(PDO $pdo, int $id): void
 {
-    $stmt = $pdo->prepare('SELECT * FROM scope_templates WHERE id = ?');
+    $stmt = $pdo->prepare(
+        'SELECT id, name, title, description FROM scope_templates WHERE id = ?'
+    );
     $stmt->execute([$id]);
     $template = $stmt->fetch();
 
@@ -114,7 +121,10 @@ function handleGetScopeDetail(PDO $pdo, int $id): void
         errorResponse('Šablona nebyla nalezena', 404);
     }
 
-    $stmt = $pdo->prepare('SELECT * FROM scope_template_sections WHERE scope_template_id = ? ORDER BY position');
+    $stmt = $pdo->prepare(
+        'SELECT id, scope_template_id, position, title, title_cz, content
+        FROM scope_template_sections WHERE scope_template_id = ? ORDER BY position'
+    );
     $stmt->execute([$id]);
     $template['sections'] = $stmt->fetchAll();