refactor: centralize custom interaction IDs into constants

Replace all hardcoded custom ID strings with module-level constants.
Each module now has *_CUSTOM_IDS in its types file, using functions
for dynamic IDs and PREFIX for startsWith matching.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

bot/commands/admin/prune.ts

@@ -11,6 +11,7 @@ import {
     getCancelledEmbed
 } from "@/modules/moderation/prune.view";
 import { withCommandErrorHandling } from "@lib/commandUtils";
+import { PRUNE_CUSTOM_IDS } from "@modules/moderation/prune.types";
 
 export const prune = createCommand({
     data: new SlashCommandBuilder()
@@ -83,7 +84,7 @@ export const prune = createCommand({
                             time: 30000
                         });
 
-                        if (confirmation.customId === "cancel_prune") {
+                        if (confirmation.customId === PRUNE_CUSTOM_IDS.CANCEL) {
                             await confirmation.update({
                                 embeds: [getCancelledEmbed()],
                                 components: []