feat: add support for broadcast replay configuration (#805)

Added ReplayOption struct and replay field to BroadcastJoinConfig
to support configuring broadcast replay with 'since' timestamp and optional
'limit' parameter. Broadcast callbacks will automatically receive meta field
with replayed status and message id when replay is enabled.

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-authored-by: Claude <[email protected]>

Author: grdsdev

Sources/Realtime/RealtimeJoinConfig.swift

@@ -33,17 +33,44 @@ struct RealtimeJoinConfig: Codable, Hashable {
   }
 }
 
+/// Configuration for broadcast replay feature.
+/// Allows replaying broadcast messages from a specific timestamp.
+public struct ReplayOption: Codable, Hashable, Sendable {
+  /// Unix timestamp (in milliseconds) from which to start replaying messages
+  public var since: Int
+  /// Optional limit on the number of messages to replay
+  public var limit: Int?
+
+  public init(since: Int, limit: Int? = nil) {
+    self.since = since
+    self.limit = limit
+  }
+}
+
 public struct BroadcastJoinConfig: Codable, Hashable, Sendable {
   /// Instructs server to acknowledge that broadcast message was received.
   public var acknowledgeBroadcasts: Bool = false
   /// Broadcast messages back to the sender.
   ///
   /// By default, broadcast messages are only sent to other clients.
   public var receiveOwnBroadcasts: Bool = false
+  /// Configures broadcast replay from a specific timestamp
+  public var replay: ReplayOption?
+
+  public init(
+    acknowledgeBroadcasts: Bool = false,
+    receiveOwnBroadcasts: Bool = false,
+    replay: ReplayOption? = nil
+  ) {
+    self.acknowledgeBroadcasts = acknowledgeBroadcasts
+    self.receiveOwnBroadcasts = receiveOwnBroadcasts
+    self.replay = replay
+  }
 
   enum CodingKeys: String, CodingKey {
     case acknowledgeBroadcasts = "ack"
     case receiveOwnBroadcasts = "self"
+    case replay
   }
 }