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/screens/Settings.svelte

@@ -11,22 +11,12 @@
   import type { ThemePref } from '../lib/theme';
   import type { BoardLabelMode } from '../lib/boardlabels';
   import { insideTelegram } from '../lib/telegram';
-  import { insideVK } from '../lib/vk';
-  import { offlineMode, setOfflineMode, requestOffline } from '../lib/offline.svelte';
-  import { isStandalone } from '../lib/pwa';
   import InstallApp from '../components/InstallApp.svelte';
 
   // The board-zoom toggle only makes sense on a touch device (the desktop / landscape layouts fit
   // the whole board and never auto-zoom), so it is shown only for a coarse pointer.
   const coarsePointer = typeof matchMedia !== 'undefined' && matchMedia('(pointer: coarse)').matches;
 
-  // The offline toggle is for the installed web PWA with a confirmed email only: the service worker
-  // that lets the app launch with no network runs only in a standalone web install (not a mini-app),
-  // and a durable account (email) anchors the device-local games. Elsewhere the control is hidden.
-  const offlineEligible = $derived(
-    isStandalone() && !insideTelegram() && !insideVK() && !!app.profile?.email,
-  );
-
   const themes: ThemePref[] = ['auto', 'light', 'dark'];
   const themeLabel: Record<ThemePref, MessageKey> = {
     auto: 'settings.themeAuto',
@@ -41,24 +31,6 @@
     none: 'settings.labelsNone',
   };
 
-  // The offline toggle gates entry on dictionary readiness: flipping to offline fetches the enabled
-  // variants' dictionaries (cache-first) and waits at most a few seconds; if they cannot be made
-  // available it stays online and shows the "needs internet" note, while the fetch keeps warming the
-  // cache in the background so a later flip is instant. Leaving offline (-> online) is never gated.
-  let checking = $state(false);
-  let needsData = $state(false);
-
-  async function goOffline(): Promise<void> {
-    if (offlineMode.active || checking) return;
-    needsData = false;
-    checking = true;
-    try {
-      const ready = await requestOffline(app.profile);
-      if (!ready) needsData = true;
-    } finally {
-      checking = false;
-    }
-  }
 </script>
 
 <div class="page">
@@ -119,33 +91,6 @@
     {/if}
   </section>
 
-  {#if offlineEligible}
-    <section>
-      <h3>{t('settings.offlineMode')}</h3>
-      <div class="seg">
-        <button
-          class="opt"
-          class:active={!offlineMode.active}
-          disabled={checking}
-          onclick={() => {
-            needsData = false;
-            setOfflineMode(false);
-          }}
-        >
-          {t('settings.online')}
-        </button>
-        <button class="opt" class:active={offlineMode.active} disabled={checking} onclick={goOffline}>
-          {t('settings.offline')}
-        </button>
-      </div>
-      {#if checking}
-        <p class="onote">{t('settings.offlineChecking')}</p>
-      {:else if needsData}
-        <p class="onote onote--warn" role="alert">{t('settings.offlineNeedsData')}</p>
-      {/if}
-    </section>
-  {/if}
-
   <!-- Web-only install call-to-action at the bottom of Settings (renders nothing unless the app
        is installable here — see components/InstallApp.svelte / lib/pwa). -->
   <InstallApp />
@@ -190,14 +135,6 @@
     opacity: 0.55;
     cursor: default;
   }
-  .onote {
-    font-size: 0.85rem;
-    color: var(--text-muted);
-    margin: 8px 0 0;
-  }
-  .onote--warn {
-    color: var(--warn);
-  }
   .row {
     display: flex;
     align-items: center;