feat: Implement spam protection with configurable limits and auto-mute escalation

src/EchoHub.Server/Config/SpamOptions.cs

@@ -0,0 +1,50 @@
+namespace EchoHub.Server.Config;
+
+/// <summary>
+/// Anti-spam thresholds, bound from the "Spam" config section. Defaults are lenient enough
+/// that a fast typist never trips them; Mods and above are always exempt.
+/// </summary>
+public sealed class SpamOptions
+{
+    /// <summary>Master switch for all spam protection.</summary>
+    public bool Enabled { get; set; } = true;
+
+    /// <summary>Max messages a user may send per <see cref="WindowSeconds"/> window.</summary>
+    public int MaxMessagesPerWindow { get; set; } = 8;
+
+    public int WindowSeconds { get; set; } = 5;
+
+    /// <summary>
+    /// How many identical messages in a row are tolerated; the next one is rejected.
+    /// (End-to-end encrypted rooms are naturally exempt — identical plaintext produces
+    /// different ciphertext per message, so repeats never look identical to the server.)
+    /// </summary>
+    public int MaxDuplicateMessages { get; set; } = 3;
+
+    /// <summary>
+    /// Auto-mute duration once a user accumulates <see cref="ViolationThreshold"/> rejected
+    /// sends within <see cref="ViolationWindowMinutes"/>. 0 disables auto-mute (rejections
+    /// still apply). The mute uses the normal timed-mute machinery, so moderators see it
+    /// and <c>MuteExpirationService</c> lifts it.
+    /// </summary>
+    public int AutoMuteMinutes { get; set; } = 5;
+
+    public int ViolationThreshold { get; set; } = 5;
+
+    public int ViolationWindowMinutes { get; set; } = 5;
+
+    /// <summary>
+    /// Max *first-time* channel joins per <see cref="JoinWindowSeconds"/> window. Joins of
+    /// channels the user already belongs to (reconnect/auto-join) never count, but a brand-new
+    /// user's first connect joins every public channel at once — keep this above your public
+    /// channel count.
+    /// </summary>
+    public int MaxJoinsPerWindow { get; set; } = 25;
+
+    public int JoinWindowSeconds { get; set; } = 30;
+
+    /// <summary>Max channel creations per <see cref="ChannelCreateWindowMinutes"/> window.</summary>
+    public int MaxChannelCreatesPerWindow { get; set; } = 3;
+
+    public int ChannelCreateWindowMinutes { get; set; } = 10;
+}