feat: rewrite as moderation bot (Keiko)

Replaces the old AI companion bot with a full Discord moderation system.

Commands: warn, mute, unmute, kick, softban, ban, unban, prune
Logging: member join/leave, activity (messages/threads/voice), mod actions
Audit log: captures manual bans, kicks, timeouts, and unbans
Sanctions: posts to Hikari sanction API for all applicable actions

All commands are ephemeral and use Components v2. Permission and role
hierarchy checks are enforced on every applicable command.

src/events/voiceStateUpdate.ts

@@ -0,0 +1,75 @@
+/**
+ * @copyright nhcarrigan
+ * @license Naomi's Public License
+ * @author Naomi Carrigan
+ */
+/* eslint-disable unicorn/no-keyword-prefix -- oldState/newState are the established Discord.js parameter names */
+
+import { logActivity } from "../modules/logActivity.js";
+import { logger } from "../utils/logger.js";
+import type { VoiceState } from "discord.js";
+
+/**
+ * Resolves the action string for a voice state change.
+ * @param oldState - The voice state before the update.
+ * @param newState - The voice state after the update.
+ * @returns A human-readable description of the voice action.
+ */
+const resolveVoiceAction = (
+  oldState: VoiceState,
+  newState: VoiceState,
+): string => {
+  if (!oldState.channel && newState.channel) {
+    return `Joined <#${newState.channelId ?? "Unknown"}>`;
+  }
+
+  if (oldState.channel && !newState.channel) {
+    return `Left <#${oldState.channelId ?? "Unknown"}>`;
+  }
+
+  return `Moved from <#${oldState.channelId ?? "Unknown"}> to <#${newState.channelId ?? "Unknown"}>`;
+};
+
+/**
+ * Logs voice channel join, leave, and move events to the activity log channel.
+ * @param oldState - The voice state before the update.
+ * @param newState - The voice state after the update.
+ * @returns A promise that resolves when the event has been logged.
+ */
+export const onVoiceStateUpdate = async(
+  oldState: VoiceState,
+  newState: VoiceState,
+): Promise<void> => {
+  if (oldState.channelId === newState.channelId) {
+    return;
+  }
+
+  const user = newState.member?.user ?? oldState.member?.user;
+
+  if (!user || user.bot) {
+    return;
+  }
+
+  try {
+    const action = resolveVoiceAction(oldState, newState);
+
+    const fields = [
+      `**User**: ${user.username} (\`${user.id}\`)`,
+      `**Action**: ${action}`,
+    ].join("\n");
+
+    await logActivity({
+      client: user.client,
+      emoji:  "🔊",
+      fields: fields,
+      title:  "Voice State Update",
+    });
+  } catch (error) {
+    await logger.error(
+      "Failed to log voice state update",
+      error instanceof Error
+        ? error
+        : new Error(String(error)),
+    );
+  }
+};