security: clean repository without media files and sensitive data

- Removed area/ directory with 816MB of media files
- Removed sensitive FTP credentials from Git history
- Implemented .env.upload system for secure deployments
- Added comprehensive .gitignore for future protection

This commit represents a clean slate with all sensitive data removed.

backend/public/files.php

@@ -0,0 +1,17 @@
+<?php
+$dir = __DIR__ . '/../area/Paramount/Testprojekt/ads';
+$rootPath = realpath($dir);
+if (is_dir($dir) && is_readable($dir)) {
+    $files = scandir($dir);
+    echo json_encode([
+        'success' => true,
+        'files' => $files,
+        'rootPath' => $rootPath
+    ]);
+} else {
+    echo json_encode([
+        'success' => false,
+        'error' => 'Ordner nicht vorhanden oder keine Leserechte',
+        'rootPath' => $rootPath
+    ]);
+}