fix: store username on moderation_actions for retention safety

Add denormalized  column to moderation_actions so the
dashboard TARGET field survives message table purges. Backfills all
existing 217 rows. Changes: schema + autoDeleteManager + backend
repository query + migration 0017.

services/discord-gateway/src/modules/ai-moderation/autoDeleteManager.ts

@@ -197,6 +197,7 @@ async function logAutoDeleteAttempt(
       action_type: "delete_message",
       reason: result.reason,
       ...verdictToActionFields(message),
+      username: message.username,
       executed_by: "auto-delete-manager",
       status: result.deleted
         ? "executed"
@@ -262,6 +263,7 @@ export async function attemptAutoDeleteFlaggedMessage(
             reason:
               "nickname melanggar aturan server (offensive_username); pesan dibiarkan",
             ...verdictToActionFields(message),
+            username: message.username,
             executed_by: "auto-delete-manager",
             status: resetOk ? "executed" : "failed",
             error: resetOk ? null : "nickname_reset_failed",

services/discord-gateway/src/modules/command-handler/moderation.handler.ts

@@ -103,6 +103,7 @@ export class ModerationHandler {
           | "kick_user"
           | "ban_user",
         reason: payload.reason ?? null,
+        username: null,
         executed_by: payload.executed_by ?? "command-handler",
         status: "executed",
         error: null,

services/discord-gateway/src/shared/database/schema.ts

@@ -642,6 +642,7 @@ export const pgModerationActionsTable = pgTable(
     score: pgReal("score"), // 0..1 raw model score
     evidence: pgText("evidence"), // JSON array of short quoted snippets
     policy_version: pgText("policy_version"), // rules.ts policy version string
+    username: pgText("username"), // denormalized from messages table for retention safety
   },
   (table) => ({
     messageIdIdx: pgIndex("idx_moderation_actions_message_id").on(

services/discord-gateway/src/shared/database/schema/messages.ts

@@ -59,6 +59,7 @@ export const pgModerationActionsTable = pgTable(
     score: pgReal("score"), // 0..1 raw model score
     evidence: pgText("evidence"), // JSON array of short quoted snippets
     policy_version: pgText("policy_version"), // rules.ts policy version string
+    username: pgText("username"), // denormalized from messages table for retention safety
   },
   (table) => ({
     messageIdIdx: pgIndex("idx_moderation_actions_message_id").on(

services/discord-gateway/src/shared/moderation-types.ts

@@ -208,6 +208,7 @@ export interface ModerationAction {
   guild_id: string;
   action_type: ModerationActionType;
   reason: string | null;
+  username: string | null;
   executed_by: string | null;
   status: "pending" | "executed" | "failed";
   error: string | null;