feat: add maintenance_schedules table, schema, and CRUD endpoints

Co-Authored-By: Claude Sonnet 4.5 <noreply@anthropic.com>

backend/app/models/__init__.py

@@ -23,6 +23,7 @@ from .feature_flag import FeatureFlag, PlanFeatureDefault, AccountFeatureOverrid
 from .platform_setting import PlatformSetting
 from .user_pinned_tree import UserPinnedTree
 from .target_list import TargetList
+from .maintenance_schedule import MaintenanceSchedule
 
 __all__ = [
     "User",
@@ -57,4 +58,5 @@ __all__ = [
     "PlatformSetting",
     "UserPinnedTree",
     "TargetList",
+    "MaintenanceSchedule",
 ]

backend/app/models/maintenance_schedule.py

@@ -0,0 +1,45 @@
+import uuid
+from datetime import datetime, timezone
+from typing import Optional
+from sqlalchemy import String, DateTime, ForeignKey, Boolean, UniqueConstraint
+from sqlalchemy.orm import Mapped, mapped_column
+from sqlalchemy.dialects.postgresql import UUID
+from app.core.database import Base
+
+
+class MaintenanceSchedule(Base):
+    __tablename__ = "maintenance_schedules"
+    __table_args__ = (
+        UniqueConstraint("tree_id", name="uq_maintenance_schedules_tree_id"),
+    )
+
+    id: Mapped[uuid.UUID] = mapped_column(
+        UUID(as_uuid=True), primary_key=True, default=uuid.uuid4
+    )
+    tree_id: Mapped[uuid.UUID] = mapped_column(
+        UUID(as_uuid=True), ForeignKey("trees.id", ondelete="CASCADE"),
+        nullable=False, index=True
+    )
+    created_by: Mapped[Optional[uuid.UUID]] = mapped_column(
+        UUID(as_uuid=True), ForeignKey("users.id", ondelete="SET NULL"), nullable=True
+    )
+    cron_expression: Mapped[str] = mapped_column(String(100), nullable=False)
+    timezone: Mapped[str] = mapped_column(String(100), nullable=False, default="UTC")
+    target_list_id: Mapped[Optional[uuid.UUID]] = mapped_column(
+        UUID(as_uuid=True), ForeignKey("target_lists.id", ondelete="SET NULL"), nullable=True
+    )
+    is_active: Mapped[bool] = mapped_column(Boolean, nullable=False, default=True)
+    next_run_at: Mapped[Optional[datetime]] = mapped_column(
+        DateTime(timezone=True), nullable=True
+    )
+    last_run_at: Mapped[Optional[datetime]] = mapped_column(
+        DateTime(timezone=True), nullable=True
+    )
+    created_at: Mapped[datetime] = mapped_column(
+        DateTime(timezone=True), default=lambda: datetime.now(timezone.utc)
+    )
+    updated_at: Mapped[datetime] = mapped_column(
+        DateTime(timezone=True),
+        default=lambda: datetime.now(timezone.utc),
+        onupdate=lambda: datetime.now(timezone.utc),
+    )