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/company-settings-handlers.php

@@ -9,7 +9,13 @@ declare(strict_types=1);
 function getOrCreateSettings(PDO $pdo, bool $includeLogo = false): array
 {
     if ($includeLogo) {
-        $stmt = $pdo->query('SELECT * FROM company_settings LIMIT 1');
+        $stmt = $pdo->query('
+            SELECT id, company_name, company_id, vat_id, street, city, postal_code,
+                   country, quotation_prefix, default_currency, default_vat_rate,
+                   custom_fields, logo_data, uuid, modified_at, sync_version,
+                   order_type_code, invoice_type_code, is_deleted, require_2fa
+            FROM company_settings LIMIT 1
+        ');
     } else {
         $stmt = $pdo->query('
             SELECT id, company_name, company_id, vat_id, street, city, postal_code, country,