Alternate names (maiden/married), self-person link, deletion integrity

Names (the genealogy standard: maiden name primary, married/alias as typed
alternates):
- Name model already supported multiple typed names; expose full CRUD —
  NameCreate/Read/Update schemas, name_service (one-primary invariant,
  promote-on-delete), nested /persons/{id}/names routes.
- Person page gains a Names card: add/edit/delete + "make primary", with a
  curated name_type dropdown (birth/maiden, married, alias, nickname, …).

Self-person ("who am I"):
- users.self_person_id FK (use_alter for the users<->persons<->trees cycle)
  + migration; PATCH /users/me/self-person; "This is me" / "This is you"
  on the person page. Soft-deleting the linked person clears it.

Deletion integrity (fixes the broken tree view):
- delete_person now soft-deletes the relationships touching the person, so no
  dangling edges remain; family-chart also filters links to missing people.
- Optional cascade=true recursively deletes descendants (GEDCOM cleanup);
  the person page asks "only this person" vs "with all descendants".
- DELETE returns {deleted: n}.

Family view surfaces "Not connected to anyone" so dangling people aren't lost.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

backend/app/services/user_service.py

@@ -8,10 +8,13 @@ import uuid
 from sqlalchemy import select
 from sqlalchemy.ext.asyncio import AsyncSession
 
+from app.models.person import Person
+from app.models.tree import Tree
 from app.models.user import User
 from app.repositories.base import BaseRepository
+from app.services import privacy
 from app.services.audit import record_audit
-from app.services.exceptions import Conflict
+from app.services.exceptions import Conflict, Forbidden, NotFound
 
 
 async def create_user(
@@ -42,3 +45,39 @@ async def create_user(
 
 async def get_user(session: AsyncSession, user_id: uuid.UUID) -> User | None:
     return await BaseRepository(session, User).get(user_id)
+
+
+async def set_self_person(
+    session: AsyncSession, *, user: User, person_id: uuid.UUID | None
+) -> User:
+    """Point a user's account at the Person record that *is* them ("home
+    person"), or clear it with ``None``. The person must live in a tree the
+    user can view."""
+    if person_id is not None:
+        person = (
+            await session.execute(
+                select(Person).where(Person.id == person_id, Person.deleted_at.is_(None))
+            )
+        ).scalar_one_or_none()
+        if person is None:
+            raise NotFound("person not found")
+        tree = (
+            await session.execute(select(Tree).where(Tree.id == person.tree_id))
+        ).scalar_one_or_none()
+        if tree is None or not await privacy.can_view_tree(
+            session, user_id=user.id, tree=tree
+        ):
+            raise Forbidden("not permitted to link this person")
+
+    user.self_person_id = person_id
+    record_audit(
+        session,
+        action="update",
+        entity_type="User",
+        entity_id=user.id,
+        actor_user_id=user.id,
+        after={"self_person_id": str(person_id) if person_id else None},
+    )
+    await session.commit()
+    await session.refresh(user)
+    return user