i18n spiegelt die aktive Sprache auf <html lang> (Init + languageChanged;
der User-Locale-Wechsel in auth-context läuft über dasselbe Event). Neuer
useDocumentTitle-Hook setzt je Route einen sprechenden Titel
(Seite — Teich — Dorfteich), verdrahtet in allen Routen-Komponenten;
dynamische Titel folgen den geladenen Daten.
Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01AGM8jo3hwoV9wsCVGfy8iq
GET /ponds/:id/pages lists a pond's pages ordered by the pond's
persisted sidebarSort setting (alpha/created; manual arrives with #45).
The sidebar consumes it to show the page list with an active-page
highlight, an owner-only sort switch (persists via the existing
PATCH /ponds/:id), and an inline "new page" flow. The top bar gains a
pond switcher; a new /p/:pondSlug route gives it somewhere to land,
redirecting to the pond's first page once loaded. Sidebar collapse
gains a Ctrl/Cmd+\ shortcut and a slightly refined transition.
Closes#26
