feat: zodpovedna osoba za projekt - novy sloupec + editace

Pridano pole responsible_user_id do tabulky projects s FK na users.
Select zodpovedne osoby v ProjectDetail, ProjectCreate a sloupec v seznamu projektu.

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

dist/api/admin/projects.php

@@ -56,6 +56,9 @@ try {
                     requirePermission($authData, 'projects.create');
                     handleGetNextNumber($pdo);
                     break;
+                case 'users':
+                    handleGetUsers($pdo);
+                    break;
                 default:
                     handleGetList($pdo);
             }