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/note.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 { CaseType } from "@shared/lib/constants";
 import { getNoteSuccessEmbed, getModerationErrorEmbed } from "@/modules/moderation/moderation.view";
 
@@ -31,7 +31,7 @@ export const note = createCommand({
             const noteText = interaction.options.getString("note", true);
 
             // Create the note case
-            const moderationCase = await ModerationService.createCase({
+            const moderationCase = await moderationService.createCase({
                 type: CaseType.NOTE,
                 userId: targetUser.id,
                 username: targetUser.username,