feat: add target_lists table, schema, and CRUD endpoints

Introduces the TargetList model (team-scoped JSONB target arrays),
Pydantic schemas, and full CRUD REST API at /target-lists/.
Includes Alembic migration and 5 integration tests (TDD).

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

backend/app/models/__init__.py

@@ -22,6 +22,7 @@ from .account_limit_override import AccountLimitOverride
 from .feature_flag import FeatureFlag, PlanFeatureDefault, AccountFeatureOverride
 from .platform_setting import PlatformSetting
 from .user_pinned_tree import UserPinnedTree
+from .target_list import TargetList
 
 __all__ = [
     "User",
@@ -55,4 +56,5 @@ __all__ = [
     "AccountFeatureOverride",
     "PlatformSetting",
     "UserPinnedTree",
+    "TargetList",
 ]

backend/app/models/target_list.py

@@ -0,0 +1,38 @@
+import uuid
+from datetime import datetime, timezone
+from typing import Optional, TYPE_CHECKING
+from sqlalchemy import String, Text, DateTime, ForeignKey
+from sqlalchemy.orm import Mapped, mapped_column
+from sqlalchemy.dialects.postgresql import UUID, JSONB
+from app.core.database import Base
+
+if TYPE_CHECKING:
+    from app.models.user import User
+    from app.models.team import Team
+
+
+class TargetList(Base):
+    __tablename__ = "target_lists"
+
+    id: Mapped[uuid.UUID] = mapped_column(
+        UUID(as_uuid=True), primary_key=True, default=uuid.uuid4
+    )
+    team_id: Mapped[uuid.UUID] = mapped_column(
+        UUID(as_uuid=True), ForeignKey("teams.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
+    )
+    name: Mapped[str] = mapped_column(String(255), nullable=False)
+    description: Mapped[Optional[str]] = mapped_column(Text, nullable=True)
+    # targets: [{"label": "RDS-01", "notes": "optional notes"}, ...]
+    targets: Mapped[list] = mapped_column(JSONB, nullable=False, default=list)
+    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),
+    )