Add: Welcome and goodbye message module

- Add /welcome command with setchannel, add, remove, list, help
- Welcome messages on guildMemberAdd event
- Goodbye messages on guildMemberRemove event
- Auto-use Discord system channel if no custom channel set
- Variables: {user}, {username}, {server}, {membercount}
- Add welcome_message and goodbye_message to guild_settings

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

src/events/guildMemberRemove.ts

@@ -0,0 +1,34 @@
+import { Events, GuildMember, TextChannel, EmbedBuilder } from 'discord.js';
+
+export default {
+    name: Events.GuildMemberRemove,
+    async execute(member: GuildMember) {
+        const DB = (member.client as any).DB;
+        const guildId = member.guild.id;
+
+        const settings: any = DB.get('SELECT * FROM guild_settings WHERE guild_id = ?', guildId);
+
+        // Use custom channel or fall back to Discord's system channel
+        const channelId = settings?.welcome_channel || member.guild.systemChannelId;
+        if (!channelId || !settings?.goodbye_message) {
+            return;
+        }
+
+        const channel = member.guild.channels.cache.get(channelId);
+        if (!channel || !channel.isTextBased()) {
+            return;
+        }
+
+        const message = settings.goodbye_message
+            .replace(/{user}/g, `<@${member.id}>`)
+            .replace(/{username}/g, member.user.username)
+            .replace(/{server}/g, member.guild.name)
+            .replace(/{membercount}/g, member.guild.memberCount.toString());
+
+        try {
+            await (channel as TextChannel).send(message);
+        } catch (error) {
+            console.error('[WELCOME] Error sending goodbye message:', error);
+        }
+    },
+};