Person page: server-side search; stop loading the whole tree

The person page fetched the entire tree on every open — all persons (to build a
name map + power the relative pickers) and all events (to find partnership
events). On a 2k-person tree that's a ~230KB person list + ~600KB event list per
view. Now it loads only what the page shows:

Frontend:
- The relationship & spouse pickers use the backend's fuzzy pg_trgm search
  (debounced, typo-tolerant) instead of substring-filtering a preloaded array —
  better search, and no need to preload every person. PersonCombobox gained an
  `onSearch` server mode (client `people` mode still works).
- The page drops the all-persons and all-events fetches; it resolves just this
  person's relatives' names via GET /persons?ids=..., and reads partnership
  events from the per-person events endpoint.

Backend:
- GET /trees/{id}/persons?ids=a,b,c — batch by id (privacy-filtered, names
  batched), for relative-name display.
- list_events_for_person (member path) now also returns the person's partnership
  events, so the page needn't scan every event in the tree.

Adversarial review (frontend logic + backend/privacy) found no issues. Suite 105
passing.

Signed-off-by: Justin Paul <justin@jpaul.me>

backend/app/api/v1/persons.py

@@ -1,6 +1,6 @@
 import uuid
 
-from fastapi import APIRouter, status
+from fastapi import APIRouter, HTTPException, status
 
 from app.api.deps import CurrentUser, SessionDep
 from app.schemas.person import PersonCreate, PersonRead, PersonUpdate
@@ -41,9 +41,18 @@ async def list_persons(
     current: CurrentUser,
     deleted: bool = False,
     q: str | None = None,
+    ids: str | None = None,
 ) -> list[PersonRead]:
     tree = await tree_service.get_tree(session, viewer_id=current.id, tree_id=tree_id)
-    if q:
+    if ids is not None:
+        try:
+            id_list = [uuid.UUID(x) for x in ids.split(",") if x.strip()]
+        except ValueError as exc:
+            raise HTTPException(status.HTTP_422_UNPROCESSABLE_ENTITY, "invalid ids") from exc
+        persons = await person_service.list_persons_by_ids(
+            session, viewer_id=current.id, tree=tree, ids=id_list
+        )
+    elif q:
         persons = await person_service.search_persons(
             session, viewer_id=current.id, tree=tree, query=q
         )