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/models/user.py

@@ -0,0 +1,20 @@
+from sqlalchemy import Column, Integer, String, DateTime
+from datetime import datetime
+import pytz
+from utils.auth import Base
+
+class AdminUser(Base):
+    """
+    SQLAlchemy model representing an admin user.
+
+    Attributes:
+        id (int): Primary key identifier.
+        username (str): Unique admin username.
+        password_hash (str): Hashed password for authentication.
+        created_at (datetime): Timestamp of account creation (stored in Europe/Bratislava timezone).
+    """
+    __tablename__ = "admin_users"
+    id = Column(Integer, primary_key=True)
+    username = Column(String, unique=True, nullable=False)
+    password_hash = Column(String, nullable=False)
+    created_at = Column(DateTime, default=lambda: datetime.now(pytz.timezone('Europe/Bratislava')))