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).

gateway/internal/config/config.go

@@ -60,6 +60,11 @@ type Config struct {
 	// "update required" signal before its payload is decoded. Empty leaves the gate dormant
 	// (every client is served) — the default for web-only deployments.
 	MinClientVersion string
+	// RecommendedClientVersion, when non-empty, is the version below which a served client is nudged
+	// to update — a non-blocking "update available" signal (the X-Update-Recommended response header)
+	// on gated responses; the call still succeeds. It must be at least MinClientVersion. Empty leaves
+	// the soft tier off (the default); it does not affect the hard MinClientVersion gate.
+	RecommendedClientVersion string
 	// RateLimit configures the in-memory anti-abuse limiter.
 	RateLimit RateLimitConfig
 	// Abuse configures the temporary IP ban and the honeytoken (prod-only).
@@ -232,15 +237,16 @@ func (c VKIDConfig) Enabled() bool {
 func Load() (Config, error) {
 	var err error
 	c := Config{
-		HTTPAddr:         envOr("GATEWAY_HTTP_ADDR", defaultHTTPAddr),
-		LogLevel:         envOr("GATEWAY_LOG_LEVEL", defaultLogLevel),
-		BackendHTTPURL:   envOr("GATEWAY_BACKEND_HTTP_URL", defaultBackendHTTPURL),
-		BackendGRPCAddr:  envOr("GATEWAY_BACKEND_GRPC_ADDR", defaultBackendGRPCAddr),
-		AdminUser:        os.Getenv("GATEWAY_ADMIN_USER"),
-		AdminPassword:    os.Getenv("GATEWAY_ADMIN_PASSWORD"),
-		ValidatorAddr:    os.Getenv("GATEWAY_VALIDATOR_ADDR"),
-		VKAppSecret:      os.Getenv("GATEWAY_VK_APP_SECRET"),
-		MinClientVersion: os.Getenv("GATEWAY_MIN_CLIENT_VERSION"),
+		HTTPAddr:                 envOr("GATEWAY_HTTP_ADDR", defaultHTTPAddr),
+		LogLevel:                 envOr("GATEWAY_LOG_LEVEL", defaultLogLevel),
+		BackendHTTPURL:           envOr("GATEWAY_BACKEND_HTTP_URL", defaultBackendHTTPURL),
+		BackendGRPCAddr:          envOr("GATEWAY_BACKEND_GRPC_ADDR", defaultBackendGRPCAddr),
+		AdminUser:                os.Getenv("GATEWAY_ADMIN_USER"),
+		AdminPassword:            os.Getenv("GATEWAY_ADMIN_PASSWORD"),
+		ValidatorAddr:            os.Getenv("GATEWAY_VALIDATOR_ADDR"),
+		VKAppSecret:              os.Getenv("GATEWAY_VK_APP_SECRET"),
+		MinClientVersion:         os.Getenv("GATEWAY_MIN_CLIENT_VERSION"),
+		RecommendedClientVersion: os.Getenv("GATEWAY_RECOMMENDED_CLIENT_VERSION"),
 		VKID: VKIDConfig{
 			AppID:        os.Getenv("GATEWAY_VK_ID_APP_ID"),
 			ClientSecret: os.Getenv("GATEWAY_VK_ID_CLIENT_SECRET"),
@@ -344,6 +350,18 @@ func (c Config) validate() error {
 			return fmt.Errorf("config: GATEWAY_MIN_CLIENT_VERSION %q is not a MAJOR.MINOR.PATCH version", c.MinClientVersion)
 		}
 	}
+	if c.RecommendedClientVersion != "" {
+		rec, ok := clientver.Parse(c.RecommendedClientVersion)
+		if !ok {
+			return fmt.Errorf("config: GATEWAY_RECOMMENDED_CLIENT_VERSION %q is not a MAJOR.MINOR.PATCH version", c.RecommendedClientVersion)
+		}
+		// The soft tier must sit at or above the hard minimum: a recommended below the minimum is a
+		// misconfiguration (every client below min is already turned away). An empty/unparseable
+		// minimum imposes no lower bound, so the recommended may stand alone.
+		if min, ok := clientver.Parse(c.MinClientVersion); ok && clientver.Less(rec, min) {
+			return fmt.Errorf("config: GATEWAY_RECOMMENDED_CLIENT_VERSION %q must be >= GATEWAY_MIN_CLIENT_VERSION %q", c.RecommendedClientVersion, c.MinClientVersion)
+		}
+	}
 	if c.Abuse.BanEnabled && (c.Abuse.BanThreshold <= 0 || c.Abuse.BanWindow <= 0 || c.Abuse.BanDuration <= 0) {
 		return fmt.Errorf("config: GATEWAY_ABUSE_BAN_THRESHOLD/_WINDOW/_DURATION must be positive when GATEWAY_ABUSE_BAN_ENABLED")
 	}

gateway/internal/config/config_test.go

@@ -70,6 +70,42 @@ func TestLoadMinClientVersion(t *testing.T) {
 	}
 }
 
+// TestLoadRecommendedClientVersion verifies the soft-tier config: dormant (empty) by default, a
+// parseable version accepted (standing alone with no minimum, or at/above one), an unparseable one
+// rejected, and a recommended below the minimum rejected.
+func TestLoadRecommendedClientVersion(t *testing.T) {
+	c, err := Load()
+	if err != nil {
+		t.Fatalf("Load: %v", err)
+	}
+	if c.RecommendedClientVersion != "" {
+		t.Errorf("RecommendedClientVersion = %q, want empty (soft tier dormant)", c.RecommendedClientVersion)
+	}
+	// Stands alone with no minimum configured.
+	t.Setenv("GATEWAY_RECOMMENDED_CLIENT_VERSION", "v1.20.0")
+	if c, err = Load(); err != nil {
+		t.Fatalf("Load with a valid recommended version (no min): %v", err)
+	}
+	if c.RecommendedClientVersion != "v1.20.0" {
+		t.Errorf("RecommendedClientVersion = %q, want %q", c.RecommendedClientVersion, "v1.20.0")
+	}
+	// At or above the minimum is accepted.
+	t.Setenv("GATEWAY_MIN_CLIENT_VERSION", "v1.16.0")
+	if _, err = Load(); err != nil {
+		t.Fatalf("Load with recommended >= min: %v", err)
+	}
+	// Below the minimum is rejected.
+	t.Setenv("GATEWAY_RECOMMENDED_CLIENT_VERSION", "v1.10.0")
+	if _, err := Load(); err == nil {
+		t.Fatal("Load: expected an error for a recommended version below the minimum, got nil")
+	}
+	// Unparseable is rejected.
+	t.Setenv("GATEWAY_RECOMMENDED_CLIENT_VERSION", "dev")
+	if _, err := Load(); err == nil {
+		t.Fatal("Load: expected an error for an unparseable GATEWAY_RECOMMENDED_CLIENT_VERSION, got nil")
+	}
+}
+
 // TestLoadAbuseDefaults verifies the anti-abuse ban defaults: disabled (prod-only),
 // the agreed thresholds, and no honeytoken.
 func TestLoadAbuseDefaults(t *testing.T) {