Full-CRUD sweep: update endpoints for tree, source, citation, relationship, media

Closes the rule #8 gap at the API layer: PATCH endpoints + service updates for Tree (name/description/visibility), Source, Citation (page/detail/confidence), Relationship (qualifier/notes), and Media (title/attachment) — editor-gated and audited. Every core entity now has create/read/update/delete. Edit UIs for these land in the frontend batch. 37 tests pass.

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

backend/app/services/relationship_service.py

@@ -107,6 +107,44 @@ async def list_relationships_for_person(
     return list((await session.execute(stmt)).scalars().all())
 
 
+async def update_relationship(
+    session: AsyncSession, *, actor: User, tree: Tree, relationship_id: uuid.UUID, changes: dict
+) -> Relationship:
+    if not await privacy.can_edit_tree(session, user_id=actor.id, tree=tree):
+        raise Forbidden("not an editor of this tree")
+    relationship = (
+        await session.execute(
+            select(Relationship).where(
+                Relationship.id == relationship_id,
+                Relationship.tree_id == tree.id,
+                Relationship.deleted_at.is_(None),
+            )
+        )
+    ).scalar_one_or_none()
+    if relationship is None:
+        raise NotFound("relationship not found")
+    if (
+        "qualifier" in changes
+        and changes["qualifier"] is not None
+        and relationship.type is not RelationshipType.parent_child
+    ):
+        raise Conflict("qualifier only applies to parent_child relationships")
+    for key in {"qualifier", "notes"} & changes.keys():
+        setattr(relationship, key, changes[key])
+    record_audit(
+        session,
+        action="update",
+        entity_type="Relationship",
+        entity_id=relationship.id,
+        tree_id=tree.id,
+        actor_user_id=actor.id,
+        after=changes,
+    )
+    await session.commit()
+    await session.refresh(relationship)
+    return relationship
+
+
 async def delete_relationship(
     session: AsyncSession, *, actor: User, tree: Tree, relationship_id: uuid.UUID
 ) -> None: