add element pdf path

backend/database/migrations/2026_05_24_000001_elements_table.php

@@ -14,6 +14,7 @@ return new class extends Migration
             $table->string('title');
             $table->text('description')->default('');
             $table->text('rich_text')->default('');
+            $table->string('pdf_path')->nullable();
             $table->foreignId('parent_element_id')
                 ->nullable()
                 ->constrained('elements');