feat: implement security headers and rate limiting; update environment variables and documentation

backend/package.json

@@ -31,7 +31,8 @@
     "sharp": "^0.33.5",
     "tesseract.js": "^6.0.1",
     "uuid": "^11.1.0",
-    "helmet": "^8.0.0"
+    "helmet": "^8.0.0",
+    "@nestjs/throttler": "^6.4.0"
   },
   "devDependencies": {
     "@nestjs/cli": "^10.3.0",

backend/src/app.module.ts

@@ -1,5 +1,6 @@
 import { Module } from '@nestjs/common';
 import { APP_GUARD } from '@nestjs/core';
+import { ThrottlerModule, ThrottlerGuard } from '@nestjs/throttler';
 import { HealthModule } from './health/health.module';
 import { PrismaModule } from './prisma/prisma.module';
 import { ProductsModule } from './products/products.module';
@@ -21,6 +22,13 @@ import { RolesGuard } from './auth/roles.guard';
 
 @Module({
   imports: [
+    ThrottlerModule.forRoot([
+      {
+        name: 'default',
+        ttl: 60_000,   // 1 minut
+        limit: 120,    // 120 anrop per minut (generellt)
+      },
+    ]),
     HealthModule,    
     PrismaModule,
     ProductsModule,
@@ -38,6 +46,10 @@ import { RolesGuard } from './auth/roles.guard';
     AiModule,
   ],
   providers: [
+    {
+      provide: APP_GUARD,
+      useClass: ThrottlerGuard,
+    },
     {
       provide: APP_GUARD,
       useClass: JwtAuthGuard,

backend/src/auth/auth.controller.ts

@@ -1,4 +1,5 @@
 import { Controller, Post, Body, HttpCode, HttpStatus } from '@nestjs/common';
+import { Throttle } from '@nestjs/throttler';
 import { AuthService } from './auth.service';
 import { RegisterDto } from './dto/register.dto';
 import { LoginDto } from './dto/login.dto';
@@ -9,12 +10,14 @@ export class AuthController {
   constructor(private readonly authService: AuthService) {}
 
   @Public()
+  @Throttle({ default: { ttl: 60_000, limit: 10 } })
   @Post('register')
   register(@Body() dto: RegisterDto) {
     return this.authService.register(dto);
   }
 
   @Public()
+  @Throttle({ default: { ttl: 60_000, limit: 10 } })
   @HttpCode(HttpStatus.OK)
   @Post('login')
   login(@Body() dto: LoginDto) {

backend/src/auth/auth.module.ts

@@ -11,7 +11,11 @@ import { UsersModule } from '../users/users.module';
     UsersModule,
     PassportModule,
     JwtModule.register({
-      secret: process.env.JWT_SECRET ?? 'changeme',
+      secret: (() => {
+        const secret = process.env.JWT_SECRET;
+        if (!secret) throw new Error('JWT_SECRET saknas i miljövariabler');
+        return secret;
+      })(),
       signOptions: { expiresIn: '7d' },
     }),
   ],

backend/src/auth/jwt.strategy.ts

@@ -5,10 +5,12 @@ import { ExtractJwt, Strategy } from 'passport-jwt';
 @Injectable()
 export class JwtStrategy extends PassportStrategy(Strategy) {
   constructor() {
+    const secret = process.env.JWT_SECRET;
+    if (!secret) throw new Error('JWT_SECRET saknas i miljövariabler');
     super({
       jwtFromRequest: ExtractJwt.fromAuthHeaderAsBearerToken(),
       ignoreExpiration: false,
-      secretOrKey: process.env.JWT_SECRET ?? 'changeme',
+      secretOrKey: secret,
     });
   }
 

backend/src/products/products.controller.ts

@@ -13,6 +13,7 @@ import {
   Query,
   Request,
 } from '@nestjs/common';
+import { Throttle } from '@nestjs/throttler';
 import { Public } from '../auth/decorators/public.decorator';
 import { CreateProductDto } from './dto/create-product.dto';
 import { UpdateProductDto } from './dto/update-product.dto';
@@ -89,6 +90,7 @@ export class ProductsController {
 
   @Roles('admin')
   @Post('ai-categorize-bulk')
+  @Throttle({ default: { ttl: 60_000, limit: 5 } })
   @HttpCode(200)
   async aiCategorizeBulk(@Body() body: AiCategorizeBulkDto) {
     const categories = await this.categoriesService.findFlattened();
@@ -113,6 +115,7 @@ export class ProductsController {
   }
 
   @Get(':id/suggest-category')
+  @Throttle({ default: { ttl: 60_000, limit: 20 } })
   async suggestCategory(
     @Param('id', ParseIntPipe) id: number,
     @Request() req: { user: { role: string; isPremium: boolean } },

backend/src/receipt-import/receipt-import.controller.ts

@@ -7,6 +7,7 @@ import {
   UseInterceptors,
   BadRequestException,
 } from '@nestjs/common';
+import { Throttle } from '@nestjs/throttler';
 import { FileInterceptor } from '@nestjs/platform-express';
 import { memoryStorage } from 'multer';
 import { ReceiptImportService } from './receipt-import.service';
@@ -27,6 +28,7 @@ export class ReceiptImportController {
   constructor(private readonly receiptImportService: ReceiptImportService) {}
 
   @Post()
+  @Throttle({ default: { ttl: 60_000, limit: 20 } })
   @UseGuards(JwtAuthGuard)
   @UseInterceptors(
     FileInterceptor('file', {