fix(security): harden auth, upload, and API configuration

- Lock public registration to first-user bootstrap (403 afterwards)
- Require JwtAuthGuard on upload + whitelist png/jpg/webp/gif (SVG/XSS blocked)
- Add global throttling (login/register 5/min, upload 10/min)
- Add helmet security headers; serve uploads with nosniff
- Replace permissive CORS (origin:true+credentials) with CORS_ORIGINS whitelist
- Disable Swagger outside development; sanitize 500 error responses
- Enforce 32+ char JWT_SECRET; make token expiry configurable (TOKEN_EXPIRES_IN)
- Re-check user in DB on every JWT validation (revocation on user delete)
- Dummy bcrypt compare to prevent login user-enumeration via timing
- Map malformed BigInt inputs to 400 instead of 500
- Widen .gitignore to .env* and add apps/api/.env.example
- Disable Nuxt devtools and sourcemaps

apps/api/src/auth/auth.controller.ts

@@ -1,16 +1,10 @@
 import { Body, Controller, HttpCode, HttpStatus, Post } from '@nestjs/common';
-import {
-  ApiOperation,
-  ApiResponse,
-  ApiTags,
-} from '@nestjs/swagger';
+import { Throttle } from '@nestjs/throttler';
+import { ApiOperation, ApiResponse, ApiTags } from '@nestjs/swagger';
 import { AuthService } from './auth.service';
 import { LoginDto } from './dto/login.dto';
 import { RegisterDto } from './dto/register.dto';
-import {
-  LoginResponseDto,
-  UserPublicDto,
-} from './dto/auth-response.dto';
+import { LoginResponseDto, UserPublicDto } from './dto/auth-response.dto';
 
 @ApiTags('auth')
 @Controller('auth')
@@ -19,15 +13,18 @@ export class AuthController {
 
   @Post('register')
   @HttpCode(HttpStatus.CREATED)
-  @ApiOperation({ summary: 'Register a new admin user' })
+  @Throttle({ default: { limit: 5, ttl: 60_000 } })
+  @ApiOperation({ summary: 'Register the first admin user (bootstrap only)' })
   @ApiResponse({ status: 201, type: UserPublicDto })
   @ApiResponse({ status: 409, description: 'Username already exists' })
+  @ApiResponse({ status: 403, description: 'Registration is disabled once a user exists' })
   register(@Body() dto: RegisterDto): Promise<UserPublicDto> {
     return this.authService.register(dto) as unknown as Promise<UserPublicDto>;
   }
 
   @Post('login')
   @HttpCode(HttpStatus.OK)
+  @Throttle({ default: { limit: 5, ttl: 60_000 } })
   @ApiOperation({ summary: 'Login and obtain a JWT' })
   @ApiResponse({ status: 200, type: LoginResponseDto })
   @ApiResponse({ status: 401, description: 'Invalid credentials' })