refactor: convert ModerationService and PruneService from classes to singleton objects

- Convert ModerationService class to moderationService singleton
- Convert PruneService class to pruneService singleton
- Update all command files to use new singleton imports
- Update web routes to use new singleton imports
- Update tests for singleton pattern
- Remove getNextCaseId from tests (now private module function)

bot/commands/admin/cases.ts

@@ -1,6 +1,6 @@
 import { createCommand } from "@shared/lib/utils";
 import { SlashCommandBuilder, PermissionFlagsBits, MessageFlags } from "discord.js";
-import { ModerationService } from "@shared/modules/moderation/moderation.service";
+import { moderationService } from "@shared/modules/moderation/moderation.service";
 import { getCasesListEmbed, getModerationErrorEmbed } from "@/modules/moderation/moderation.view";
 
 export const cases = createCommand({
@@ -29,7 +29,7 @@ export const cases = createCommand({
             const activeOnly = interaction.options.getBoolean("active_only") || false;
 
             // Get cases for the user
-            const userCases = await ModerationService.getUserCases(targetUser.id, activeOnly);
+            const userCases = await moderationService.getUserCases(targetUser.id, activeOnly);
 
             const title = activeOnly
                 ? `⚠️ Active Cases for ${targetUser.username}`