refactor: resolve architecture disconnects and codebase weaknesses

- Consolidate eventTypes.ts as single source of truth for Redis channels:
  - Remove duplicate DiscordGatewayEvent interface from eventBroadcaster.ts
  - Replace all hardcoded channel strings with EventChannels constants
  - eventTypes.ts is no longer an orphan file

- Remove dangerous moderation action feature (selfbot safety):
  - Remove /messages/:id/moderate endpoint from backend
  - Remove moderation:action handler from commandHandler.ts
  - Remove publishFireAndForgetCommand (wrong envelope format)
  - Verified no remaining references to moderation:action in code

- Remove unused getCommandPublisher import from redis-bridge.ts

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

services/backend/src/modules/messages/messages.routes.ts

@@ -124,64 +124,5 @@ export function createMessagesRouter(): Router {
     }),
   );
 
-  // POST /api/messages/:id/moderate — Trigger moderation action via DG
-  router.post(
-    "/messages/:id/moderate",
-    asyncHandler(async (req: Request, res: Response) => {
-      const id = String(req.params.id ?? "");
-      if (!id) {
-        res.status(400).json({ error: "MISSING_ID" });
-        return;
-      }
-
-      const { actionType, reason } = (req.body ?? {}) as {
-        actionType?: string;
-        reason?: string;
-      };
-
-      const allowedActions = [
-        "delete_message",
-        "warn_user",
-        "kick_user",
-        "ban_user",
-        "mute_user",
-      ];
-
-      if (!actionType || !allowedActions.includes(actionType)) {
-        res.status(400).json({
-          error: "INVALID_ACTION",
-          message: `actionType must be one of: ${allowedActions.join(", ")}`,
-        });
-        return;
-      }
-
-      // Fetch the message to get guild/user context
-      const msg = await messagesService.getMessageById(id).catch(() => null);
-      if (!msg) {
-        res.status(404).json({ error: "MESSAGE_NOT_FOUND" });
-        return;
-      }
-
-      // Publish command to DG via Redis
-      const { publishCommand } = await import("../../ws/redis-bridge.js");
-      await publishCommand({
-        id: crypto.randomUUID(),
-        type: "moderation:action",
-        payload: {
-          messageId: id,
-          guildId: msg.guild_id,
-          channelId: msg.thread_id || msg.channel_id,
-          userId: msg.user_id,
-          actionType,
-          reason: reason ?? "Manual moderation from dashboard",
-          requestedAt: Date.now(),
-        },
-      });
-
-      logger.info({ id, actionType, reason }, "Moderation action dispatched");
-      res.json({ ok: true, actionType, messageId: id });
-    }),
-  );
-
   return router;
 }