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/storage/data/admins.json

@@ -0,0 +1,20 @@
+[
+    {
+        "id": 1,
+        "username": "admin",
+        "password": "$2a$12$s8EiG.SOcQm\/avdEwsX0ve9QXqW7KbKpKwQOLEZPTY1mIzY5nCUVm",
+        "role": "admin",
+        "email": "",
+        "disallowedClients": []
+    },
+    {
+        "id": 2,
+        "username": "Johannes",
+        "role": "admin",
+        "email": "j.kluge@duwfamily.de",
+        "disallowedClients": [
+            "Paramount"
+        ],
+        "password": "$2y$10$T059TgvbwRwmSOiqqhlrLeMeaxWAYZd4mT9ot\/tCTG.ldUi4pvk.K"
+    }
+]