feat(offline): implicit net-state model, two-tier version gate, unified lobby

Land the offline-model redesign (ANDROID_PLAN.md O1-O7): replace the explicit offline toggle with a single detected net-state machine, unify the lobby, and add a two-tier client-version gate. Contour-safe: both version vars empty => dormant, and the wire change is additive, so web/pwa/vk/tg behaviour is unchanged unless the gate is deliberately configured.

O1 pure net-state reducer (test-first). O2 reactive store + event wiring (connection/offline become thin shims; +@capacitor/network). O3 remove the offline toggle + migrate the pref. O4 two-tier gate: hard update_required degrades to an offline Update/Play-offline notice (not terminal); soft GATEWAY_RECOMMENDED_CLIENT_VERSION -> X-Update-Recommended nudge. O5 unified lobby (device-local + greyed-from-cache server games; self-set identity; closes G-step-0). O6 create flows (with-friends online/offline segment + offline dict guard). O7 docs (ARCHITECTURE, FUNCTIONAL +_ru, TESTING, deploy/README).

Also disable the manual android-build CI workflow for now (rename to .disabled); the Android APK release comes later.

Tests: gateway go green, svelte-check 0/0, vitest 617, e2e 122/122 (chromium + webkit).

ui/src/lib/lobbycache.ts

@@ -10,18 +10,15 @@ interface LobbySnapshot {
   games: GameView[];
   invitations: Invitation[];
   incoming: AccountRef[];
-  // Which mode the snapshot belongs to (offline = device-local games, online = server games). The
-  // lobby renders it instantly only when it matches the current mode, so a mode flip never flashes —
-  // or lets the player open — the other mode's games before the background refresh replaces them.
-  offline: boolean;
 }
 
 let snapshot: LobbySnapshot | null = null;
 
-/** getLobby returns the last lobby lists for the given mode, or null before the first load or when
- *  the cached snapshot belongs to the other mode (so the lobby cold-renders after a mode flip). */
-export function getLobby(offline: boolean): LobbySnapshot | null {
-  return snapshot && snapshot.offline === offline ? snapshot : null;
+/** getLobby returns the last lobby lists, or null before the first load. The unified lobby caches one
+ *  snapshot (device-local + server games merged); offline reuses its server games, greyed, and drops
+ *  the local ones for a fresh device read. */
+export function getLobby(): LobbySnapshot | null {
+  return snapshot;
 }
 
 /** setLobby stores the latest lobby lists. */