feat(profile): advertise per-variant dictionary versions for offline preload

The Profile now carries dict_versions (game variant -> current dictionary
version), populated from the dictionary registry at the profileResponse
choke point, so an installed PWA can preload the matching dawg per enabled
variant off the existing cold-start profile request instead of adding a
round-trip for a rare feature.

Wire path: FBS DictVersion table + Profile.dict_versions (additive,
backward-compatible trailing field) -> backend dto/registry -> gateway
ProfileResp + FBS encoder -> client codec decode into a per-variant map on
model.Profile. Empty in a degenerate no-dictionary deployment; the mock
serves v1.3.0 for all three variants. Codec decode covered by a
bite-tested round-trip unit test.

ui/src/lib/mock/data.ts

@@ -42,6 +42,9 @@ export const PROFILE: Profile = {
   email: 'you@example.com',
   telegramLinked: false,
   vkLinked: false,
+  // Every variant's current dictionary version, as the backend advertises it on the profile —
+  // the offline preloader targets `variant@version`.
+  dictVersions: { erudit_ru: 'v1.3.0', scrabble_ru: 'v1.3.0', scrabble_en: 'v1.3.0' },
 };
 
 // Seed social/account data for the mock (pnpm start + Playwright). The mock profile