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/api/v1/persons.py

@@ -75,12 +75,21 @@ async def update_person(
     return PersonRead.model_validate(person)
 
 
-@router.delete("/{tree_id}/persons/{person_id}", status_code=status.HTTP_204_NO_CONTENT)
+@router.delete("/{tree_id}/persons/{person_id}")
 async def delete_person(
-    tree_id: uuid.UUID, person_id: uuid.UUID, session: SessionDep, current: CurrentUser
-) -> None:
+    tree_id: uuid.UUID,
+    person_id: uuid.UUID,
+    session: SessionDep,
+    current: CurrentUser,
+    cascade: bool = False,
+) -> dict[str, int]:
+    """Delete a person. ``cascade=true`` also deletes all descendants. Returns
+    the number of persons deleted (1 unless cascading)."""
     tree = await tree_service.get_tree(session, viewer_id=current.id, tree_id=tree_id)
-    await person_service.delete_person(session, actor=current, tree=tree, person_id=person_id)
+    deleted = await person_service.delete_person(
+        session, actor=current, tree=tree, person_id=person_id, cascade=cascade
+    )
+    return {"deleted": deleted}
 
 
 @router.post("/{tree_id}/persons/{person_id}/restore", response_model=PersonRead)