feat: migrate frontend to Astro + expand AI moderation + backend admin/runtime config

Frontend:
- migrate from Vite to Astro (astro.config.mjs, pages/, layouts/)
- add admin panel, settings page, command palette, error boundary
- refactor App.tsx, MascotChatbot, Sidebar, Header, DashboardLayout
- update API client, WebSocket, auth, dashboard features

Backend:
- add admin module and config routes
- refactor middlewares, Redis connection, WebSocket server/bridge
- add runtime config loader

Discord Gateway:
- refactor AI moderation: circuit breaker, concurrency limiter, fallback processor
- add media analysis client, Seaxng search, user profile learner
- add new drizzle migration

Shared:
- extend database schema, add new config fields

services/backend/src/modules/mascot-chat/mascot-chat.controller.ts

@@ -1,6 +1,7 @@
 import { createChildLogger } from "@bete/shared/logger";
 import type { Request, Response } from "express";
 import { asyncHandler } from "../../shared/middlewares/index.js";
+import { chatRequestSchema } from "./mascot-chat.schema.js";
 import { mascotChatService } from "./mascot-chat.service.js";
 
 const logger = createChildLogger("mascot-chat.controller");
@@ -11,15 +12,18 @@ interface AuthenticatedRequest extends Request {
 
 export const handleMascotChat = asyncHandler(
   async (req: Request, res: Response) => {
-    const { message, context } = req.body;
-
-    if (!message || typeof message !== "string") {
+    // Validate request body against schema
+    const parsed = chatRequestSchema.safeParse(req.body);
+    if (!parsed.success) {
       return res.status(400).json({
         error: "INVALID_INPUT",
-        message: "Message is required and must be a string",
+        message: "Invalid request body",
+        details: parsed.error.flatten().fieldErrors,
       });
     }
 
+    const { message, context } = parsed.data;
+
     // Get user ID from auth middleware (if available)
     const userId = (req as AuthenticatedRequest).userId || "anonymous";