perf(ui): deprioritise the dictionary download; drop the lobby prefetch

On a slow link (EDGE) the background dictionary download starved the game's own
traffic — the board and the move preview stalled behind a 450KB fetch. Fetch the
dawg at low priority (Priority Hints; ignored on iOS WebKit, harmless) so the
browser schedules it behind the game's requests, and load it only on game open —
the lobby no longer prefetches, which was its main competitor for the channel.
Evict a cached blob the reader rejects (a stale or partial entry) so it self-heals
instead of lingering and re-fetches. Raise the app-entry bundle budget to 110KB
(the feature's small in-entry game/debug wiring; the heavy dict code stays lazy).

ui/scripts/bundle-size.mjs

@@ -19,8 +19,10 @@ import { join } from 'node:path';
 
 const DIST = 'dist';
 
-// Per-chunk gzip budgets in KB.
-const BUDGET = { app: 100, shared: 30, landing: 5 };
+// Per-chunk gzip budgets in KB. The app entry was raised to 110 when the local
+// move-preview wiring landed (the heavy dict subsystem stays in lazy chunks; this
+// covers the small in-entry game/debug wiring it needs).
+const BUDGET = { app: 110, shared: 30, landing: 5 };
 
 // gzipped returns the gzipped byte size of a built asset, or 0 when the reference is not a
 // local file (e.g. the Telegram SDK loaded from a CDN) or is missing.