feat(session): 实现同平台抢登互踢功能，优化会话踢下线逻辑

新增同平台会话踢下线能力，将iOS/Android/mobile归为同一移动分组，web仅匹配web；扩展会话存储接口支持按平台、带原因踢除会话，同步更新集群广播逻辑与各调用点，统一传递踢下线原因参数

server/utils.go

@@ -741,6 +741,27 @@ func platformFromUA(ua string) string {
 	return ""
 }
 
+// sameEvictPlatform reports whether two session platforms belong to the same
+// eviction group for same-platform login eviction (顶号互踢): identical
+// identifiers match, and ios/android/mobile are all treated as one mobile group
+// (an iOS login evicts Android sessions and vice versa). Web only matches web.
+func sameEvictPlatform(a, b string) bool {
+	if a == "" || b == "" {
+		return false
+	}
+	if strings.EqualFold(a, b) {
+		return true
+	}
+	switch strings.ToLower(a) {
+	case "ios", "android", "mobile":
+		switch strings.ToLower(b) {
+		case "ios", "android", "mobile":
+			return true
+		}
+	}
+	return false
+}
+
 func parseTLSConfig(tlsEnabled bool, jsconfig json.RawMessage) (*tls.Config, error) {
 	type tlsAutocertConfig struct {
 		// Domains to support by autocert