Add channel system with CLI, Telegram, and Web channel implementations

Define channel abstractions (IChannel, IChannelManager) with event-driven
message and connection handling. Implement ChannelManager for multi-channel
orchestration, CliChannel for terminal I/O, TelegramChannel with adapter
pattern for bot API integration, and WebChannel stub. Includes DI
registration and channel type enumeration.

Luna.Channels.Abstractions/ChannelMessageReceivedEventArgs.cs

@@ -0,0 +1,25 @@
+using Luna.Shared;
+
+namespace Luna.Channels.Abstractions;
+
+/// <summary>
+/// Event arguments for when a message is received from a channel
+/// </summary>
+public class ChannelMessageReceivedEventArgs : EventArgs
+{
+    /// <summary>
+    /// The received message
+    /// </summary>
+    public required ChannelMessage Message { get; init; }
+
+    /// <summary>
+    /// The channel that received the message
+    /// </summary>
+    public required IChannel Channel { get; init; }
+
+    /// <summary>
+    /// Set to true to indicate the message has been handled and should not be processed further
+    /// </summary>
+    public bool IsHandled { get; set; }
+
+}