added burger menu with admin page and user invitation link generation

src/baby_monitor/models/invitation.py

@@ -0,0 +1,35 @@
+"""Invitation token model for user registration.
+
+Note: DateTime(timezone=True) is used for PostgreSQL compatibility.
+SQLite will store as naive UTC, which is handled in the repository layer.
+"""
+
+from datetime import datetime
+from sqlalchemy import Boolean, DateTime, Integer, String
+from sqlalchemy.orm import Mapped, mapped_column
+
+from baby_monitor.repositories.dependencies.get_database import Base
+
+
+class Invitation(Base):
+    """Invitation token for new user registration."""
+
+    __tablename__ = "invitations"
+
+    id: Mapped[int] = mapped_column(
+        Integer, primary_key=True, autoincrement=True
+    )
+    token: Mapped[str] = mapped_column(String, unique=True, nullable=False)
+    created_at: Mapped[datetime] = mapped_column(
+        DateTime(timezone=True), nullable=False
+    )
+    expires_at: Mapped[datetime] = mapped_column(
+        DateTime(timezone=True), nullable=False
+    )
+    created_by_user_id: Mapped[int] = mapped_column(Integer, nullable=False)
+    is_consumed: Mapped[bool] = mapped_column(
+        Boolean, default=False, nullable=False
+    )
+    consumed_at: Mapped[datetime | None] = mapped_column(
+        DateTime(timezone=True), nullable=True
+    )