Add events and relationships API (Phase 1: flesh out the graph)

Events (create/list-per-person/soft-delete) and relationships (create/list-per-person/soft-delete) through the layered stack: editor-gated writes, privacy-engine reads, audit on every change. Events carry exactly one subject (person XOR partnership); relationships are typed qualified edges (parent_child gets a biological/adoptive/step/foster/donor/guardian qualifier). Adds a single-person GET. 18 tests pass.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
Signed-off-by: Justin Paul <justin@jpaul.me>

backend/app/api/v1/relationships.py

@@ -0,0 +1,50 @@
+import uuid
+
+from fastapi import APIRouter, status
+
+from app.api.deps import CurrentUser, SessionDep
+from app.schemas.relationship import RelationshipCreate, RelationshipRead
+from app.services import relationship_service, tree_service
+
+router = APIRouter(prefix="/trees", tags=["relationships"])
+
+
+@router.post(
+    "/{tree_id}/relationships",
+    response_model=RelationshipRead,
+    status_code=status.HTTP_201_CREATED,
+)
+async def create_relationship(
+    tree_id: uuid.UUID, data: RelationshipCreate, session: SessionDep, current: CurrentUser
+) -> RelationshipRead:
+    tree = await tree_service.get_tree(session, viewer_id=current.id, tree_id=tree_id)
+    relationship = await relationship_service.create_relationship(
+        session, actor=current, tree=tree, **data.model_dump()
+    )
+    return RelationshipRead.model_validate(relationship)
+
+
+@router.get(
+    "/{tree_id}/persons/{person_id}/relationships",
+    response_model=list[RelationshipRead],
+)
+async def list_person_relationships(
+    tree_id: uuid.UUID, person_id: uuid.UUID, session: SessionDep, current: CurrentUser
+) -> list[RelationshipRead]:
+    tree = await tree_service.get_tree(session, viewer_id=current.id, tree_id=tree_id)
+    rels = await relationship_service.list_relationships_for_person(
+        session, viewer_id=current.id, tree=tree, person_id=person_id
+    )
+    return [RelationshipRead.model_validate(r) for r in rels]
+
+
+@router.delete(
+    "/{tree_id}/relationships/{relationship_id}", status_code=status.HTTP_204_NO_CONTENT
+)
+async def delete_relationship(
+    tree_id: uuid.UUID, relationship_id: uuid.UUID, session: SessionDep, current: CurrentUser
+) -> None:
+    tree = await tree_service.get_tree(session, viewer_id=current.id, tree_id=tree_id)
+    await relationship_service.delete_relationship(
+        session, actor=current, tree=tree, relationship_id=relationship_id
+    )