fix: Response wrapping, error logging, and controller hardening (COA 3)

- HttpExceptionFilter: Log actual error details for non-HttpExceptions (was silently swallowing 500s)
- ServersService: Return null fields instead of 404 for new licenses without servers
- NotificationsController: Wrap config responses as { config } to match frontend expectations
- WebstoreController: Wrap config responses as { config } to match frontend expectations
- ChatController: Replace ParseIntPipe with manual parseInt (400 on missing optional param)
- WipesController: Same ParseIntPipe fix for history limit param

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

backend-nest/src/modules/chat/chat.controller.ts

@@ -1,4 +1,4 @@
-import { Controller, Get, Put, Param, Body, Query, ParseIntPipe, UseGuards } from '@nestjs/common';
+import { Controller, Get, Put, Param, Body, Query, UseGuards } from '@nestjs/common';
 import { ApiTags, ApiBearerAuth, ApiOperation, ApiQuery } from '@nestjs/swagger';
 import { ChatService } from './chat.service';
 import { FlagMessageDto } from './dto/flag-message.dto';
@@ -21,9 +21,10 @@ export class ChatController {
   @ApiQuery({ name: 'limit', required: false, example: 100 })
   async getMessages(
     @CurrentTenant() licenseId: string,
-    @Query('limit', new ParseIntPipe({ optional: true })) limit?: number,
+    @Query('limit') limit?: string,
   ) {
-    return await this.chatService.getMessages(licenseId, limit || 100);
+    const limitNum = limit ? parseInt(limit, 10) : 100;
+    return await this.chatService.getMessages(licenseId, limitNum);
   }
 
   @Put(':id/flag')