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/bank-accounts-handlers.php

@@ -4,7 +4,11 @@ declare(strict_types=1);
 
 function handleGetBankAccountList(PDO $pdo): void
 {
-    $stmt = $pdo->query('SELECT * FROM bank_accounts ORDER BY position, id');
+    $stmt = $pdo->query(
+        'SELECT id, account_name, bank_name, account_number, iban, bic,
+                currency, is_default, position, created_at, modified_at
+        FROM bank_accounts ORDER BY position, id'
+    );
     successResponse($stmt->fetchAll());
 }
 
@@ -78,7 +82,11 @@ function handleCreateBankAccount(PDO $pdo): void
 
 function handleUpdateBankAccount(PDO $pdo, int $id): void
 {
-    $stmt = $pdo->prepare('SELECT * FROM bank_accounts WHERE id = ?');
+    $stmt = $pdo->prepare(
+        'SELECT id, account_name, bank_name, account_number, iban, bic,
+                currency, is_default, position
+        FROM bank_accounts WHERE id = ?'
+    );
     $stmt->execute([$id]);
     $account = $stmt->fetch();
 
@@ -145,7 +153,7 @@ function handleUpdateBankAccount(PDO $pdo, int $id): void
 
 function handleDeleteBankAccount(PDO $pdo, int $id): void
 {
-    $stmt = $pdo->prepare('SELECT * FROM bank_accounts WHERE id = ?');
+    $stmt = $pdo->prepare('SELECT id, account_name FROM bank_accounts WHERE id = ?');
     $stmt->execute([$id]);
     $account = $stmt->fetch();