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/offers-pdf.php

@@ -38,7 +38,12 @@ if (!$id) {
 try {
     $pdo = db();
 
-    $stmt = $pdo->prepare('SELECT * FROM quotations WHERE id = ?');
+    $stmt = $pdo->prepare(
+        'SELECT id, quotation_number, project_code, customer_id, created_at,
+                valid_until, currency, language, vat_rate, apply_vat,
+                exchange_rate, scope_title, scope_description
+        FROM quotations WHERE id = ?'
+    );
     $stmt->execute([$id]);
     $quotation = $stmt->fetch();
     if (!$quotation) {
@@ -48,20 +53,36 @@ try {
 
     $customer = null;
     if ($quotation['customer_id']) {
-        $stmt = $pdo->prepare('SELECT * FROM customers WHERE id = ?');
+        $stmt = $pdo->prepare(
+            'SELECT id, name, street, city, postal_code, country,
+                    company_id, vat_id, custom_fields
+            FROM customers WHERE id = ?'
+        );
         $stmt->execute([$quotation['customer_id']]);
         $customer = $stmt->fetch();
     }
 
-    $stmt = $pdo->prepare('SELECT * FROM quotation_items WHERE quotation_id = ? ORDER BY position');
+    $stmt = $pdo->prepare(
+        'SELECT id, quotation_id, position, description, item_description,
+                quantity, unit, unit_price, is_included_in_total
+        FROM quotation_items WHERE quotation_id = ? ORDER BY position'
+    );
     $stmt->execute([$id]);
     $items = $stmt->fetchAll();
 
-    $stmt = $pdo->prepare('SELECT * FROM scope_sections WHERE quotation_id = ? ORDER BY position');
+    $stmt = $pdo->prepare(
+        'SELECT id, quotation_id, position, title, title_cz, content
+        FROM scope_sections WHERE quotation_id = ? ORDER BY position'
+    );
     $stmt->execute([$id]);
     $sections = $stmt->fetchAll();
 
-    $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, custom_fields, logo_data,
+                quotation_prefix, default_currency, default_vat_rate
+        FROM company_settings LIMIT 1'
+    );
     $settings = $stmt->fetch();
 
     $logoBase64 = '';