refactor: migrate all code to use getGuildConfig() for guild settings

- Update all commands and events to fetch guild config once per execution
- Pass config to service methods that need it (ModerationService.issueWarning)
- Update terminal service to use guildSettingsService for persistence
- Remove direct imports of config for guild-specific settings

This consolidates configuration to database-backed guild settings,
eliminating the dual config system.

bot/events/guildMemberAdd.ts

@@ -1,20 +1,26 @@
 import { Events } from "discord.js";
 import type { Event } from "@shared/lib/types";
-import { config } from "@shared/lib/config";
+import { getGuildConfig } from "@shared/lib/config";
 import { userService } from "@shared/modules/user/user.service";
 
-// Visitor role 
 const event: Event<Events.GuildMemberAdd> = {
     name: Events.GuildMemberAdd,
     execute: async (member) => {
         console.log(`👤 New member joined: ${member.user.tag} (${member.id})`);
+        
+        const guildConfig = await getGuildConfig(member.guild.id);
+        
         try {
             const user = await userService.getUserById(member.id);
 
             if (user && user.class) {
                 console.log(`🔄 Returning student detected: ${member.user.tag}`);
-                await member.roles.remove(config.visitorRole);
-                await member.roles.add(config.studentRole);
+                if (guildConfig.visitorRole) {
+                    await member.roles.remove(guildConfig.visitorRole);
+                }
+                if (guildConfig.studentRole) {
+                    await member.roles.add(guildConfig.studentRole);
+                }
 
                 if (user.class.roleId) {
                     await member.roles.add(user.class.roleId);
@@ -22,8 +28,10 @@ const event: Event<Events.GuildMemberAdd> = {
                 }
                 console.log(`Restored student role to ${member.user.tag}`);
             } else {
-                await member.roles.add(config.visitorRole);
-                console.log(`Assigned visitor role to ${member.user.tag}`);
+                if (guildConfig.visitorRole) {
+                    await member.roles.add(guildConfig.visitorRole);
+                    console.log(`Assigned visitor role to ${member.user.tag}`);
+                }
             }
             console.log(`User Roles: ${member.roles.cache.map(role => role.name).join(", ")}`);
         } catch (error) {