Account menu + Settings (change password); per-tree home person; full-width tree

- Sidebar bottom-left now shows the signed-in user; clicking opens a menu with
  Settings and Sign out. New /settings page: account info + change password
  (POST /auth/change-password, re-verifies current password). Export/restore/
  delete are stubbed there for the next pass.
- Per-tree default/home person: tree.home_person_id (migration) + TreeUpdate/
  Read; the tree and family views open focused on it; the person page gets a
  "Set as default" control and "Default person" badge. Cleared if that person
  is deleted. Complements the account-level "this is me" link.
- Tree visualization now fills the content area (AppShell drops the max-width
  column on the /tree route); other pages stay centered.
- Audit records are coerced JSON-safe (UUIDs/enums), so PATCHing UUID fields
  like home_person_id audits cleanly.

50 backend tests pass; migration up/down verified; frontend builds.

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

frontend/app/trees/[id]/tree/page.tsx

@@ -50,16 +50,20 @@ export default function TreePage() {
         router.push("/login");
         return;
       }
-      const [r, e] = await Promise.all([
+      const [r, e, t] = await Promise.all([
         api.GET("/api/v1/trees/{tree_id}/relationships", { params: { path: { tree_id: treeId } } }),
         api.GET("/api/v1/trees/{tree_id}/events", { params: { path: { tree_id: treeId } } }),
+        api.GET("/api/v1/trees/{tree_id}", { params: { path: { tree_id: treeId } } }),
       ]);
       if (cancelled) return;
       const ppl = p.data ?? [];
+      const home = t.data?.home_person_id ?? null;
+      const homeId = home && ppl.some((x) => x.id === home) ? home : null;
       setPeople(ppl);
       setRels(r.data ?? []);
       setEvents(e.data ?? []);
-      setFocusId((cur) => cur ?? ppl[0]?.id ?? null);
+      // Open on the tree's default/home person when set, else the first person.
+      setFocusId((cur) => cur ?? homeId ?? ppl[0]?.id ?? null);
       setStatus(ppl.length ? "ready" : "empty");
     })().catch(() => !cancelled && setStatus("error"));
     return () => {