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/schemas/target_list.py

@@ -0,0 +1,34 @@
+from datetime import datetime
+from typing import Optional
+from uuid import UUID
+from pydantic import BaseModel, Field
+
+
+class TargetEntry(BaseModel):
+    label: str = Field(..., min_length=1, max_length=255)
+    notes: Optional[str] = Field(None, max_length=500)
+
+
+class TargetListCreate(BaseModel):
+    name: str = Field(..., min_length=1, max_length=255)
+    description: Optional[str] = None
+    targets: list[TargetEntry] = Field(..., min_length=1)
+
+
+class TargetListUpdate(BaseModel):
+    name: Optional[str] = Field(None, min_length=1, max_length=255)
+    description: Optional[str] = None
+    targets: Optional[list[TargetEntry]] = None
+
+
+class TargetListResponse(BaseModel):
+    id: UUID
+    team_id: UUID
+    created_by: Optional[UUID]
+    name: str
+    description: Optional[str]
+    targets: list[TargetEntry]
+    created_at: datetime
+    updated_at: datetime
+
+    model_config = {"from_attributes": True}