Fix: Rename directory to remove & character causing shell issues

Renamed ebook_backend&admin_panel to ebook_backend_admin_panel
  The & character was being interpreted by shell as background
  process operator, causing 'Dockerfile not found' errors in Coolify.

ebook_backend_admin_panel/admin-backend/utils/coupon_utils.py

@@ -0,0 +1,8 @@
+import random
+import string
+
+# def generate_coupon(length: int = 6) -> str:
+#     return ''.join(random.choices(string.ascii_uppercase + string.digits, k=length))
+
+def generate_coupon():
+    return ''.join(random.choices(string.ascii_uppercase + string.digits, k=10))