refactors

backend/models/availability.py

@@ -0,0 +1,28 @@
+from datetime import UTC, date, datetime, time
+
+from sqlalchemy import Date, DateTime, Integer, Time, UniqueConstraint
+from sqlalchemy.orm import Mapped, mapped_column
+
+from database import Base
+
+
+class Availability(Base):
+    """Admin availability slots for booking."""
+
+    __tablename__ = "availability"
+    __table_args__ = (
+        UniqueConstraint("date", "start_time", name="uq_availability_date_start"),
+    )
+
+    id: Mapped[int] = mapped_column(Integer, primary_key=True, autoincrement=True)
+    date: Mapped[date] = mapped_column(Date, nullable=False, index=True)
+    start_time: Mapped[time] = mapped_column(Time, nullable=False)
+    end_time: Mapped[time] = mapped_column(Time, nullable=False)
+    created_at: Mapped[datetime] = mapped_column(
+        DateTime(timezone=True), default=lambda: datetime.now(UTC)
+    )
+    updated_at: Mapped[datetime] = mapped_column(
+        DateTime(timezone=True),
+        default=lambda: datetime.now(UTC),
+        onupdate=lambda: datetime.now(UTC),
+    )