Grow the companion, fix idle fallback, add update banner

Companion: bump the corner mascot ~12% (128→144) and make animation
resolution robust — fall back to the idle clip when a mood has no clip of
its own, and pin the always-asleep cat to one pose so its Lottie never
reloads. This stops a bare emoji from replacing the cute companion on idle.

Update notifications: serve a build id at /api/version (a hash of the
embedded dist/index.html, which changes on every frontend deploy). The
client records its load-time id, polls every 90s (and on tab focus), and
floats a Mandarin-first "new version available" banner offering a refresh
when the id changes.

Claude-Session: https://claude.ai/code/session_016Yr6jELuRc7hyzYLccQKZd

web/src/api/client.ts

@@ -82,6 +82,10 @@ export const api = {
     req<void>(`/suggestions/${id}/accept`, { method: 'POST' }),
   dismissSuggestion: (id: string) =>
     req<void>(`/suggestions/${id}/dismiss`, { method: 'POST' }),
+
+  // Current deployed build id — changes whenever a new frontend ships. The
+  // app polls this to offer a refresh. Bypasses any cache so the answer is live.
+  version: () => req<{ version: string }>('/version', { cache: 'no-store' }),
 }
 
 // One turn in an Ask Petal conversation. History lives only in the component —