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/projects-handlers.php

@@ -114,7 +114,9 @@ function handleCreateProject(PDO $pdo): void
 
 function handleDeleteProject(PDO $pdo, int $id): void
 {
-    $stmt = $pdo->prepare('SELECT * FROM projects WHERE id = ?');
+    $stmt = $pdo->prepare(
+        'SELECT id, project_number, name, order_id, status FROM projects WHERE id = ?'
+    );
     $stmt->execute([$id]);
     $project = $stmt->fetch();
 
@@ -207,7 +209,10 @@ function handleGetList(PDO $pdo): void
 function handleGetDetail(PDO $pdo, int $id): void
 {
     $stmt = $pdo->prepare('
-        SELECT p.*,
+        SELECT p.id, p.project_number, p.name, p.customer_id,
+               p.quotation_id, p.order_id, p.status,
+               p.start_date, p.end_date, p.notes,
+               p.created_at, p.modified_at,
                c.name as customer_name,
                o.order_number, o.status as order_status,
                q.quotation_number
@@ -229,7 +234,10 @@ function handleGetDetail(PDO $pdo, int $id): void
 
 function handleUpdateProject(PDO $pdo, int $id): void
 {
-    $stmt = $pdo->prepare('SELECT * FROM projects WHERE id = ?');
+    $stmt = $pdo->prepare(
+        'SELECT id, project_number, name, status, start_date, end_date, notes
+        FROM projects WHERE id = ?'
+    );
     $stmt->execute([$id]);
     $project = $stmt->fetch();