feat(flyer-parsing): add flyer parsing module

- Added new FlyerParsingModule to the application
- Updated AppModule to import the new FlyerParsingModule
- Added new directory structure for flyer-parsing module

backend/src/flyer-parsing/flyer-parsing.controller.ts

@@ -0,0 +1,58 @@
+import {
+  BadRequestException,
+  Body,
+  Controller,
+  HttpCode,
+  Post,
+  UploadedFile,
+  UseInterceptors,
+} from '@nestjs/common';
+import { FileInterceptor } from '@nestjs/platform-express';
+import { memoryStorage } from 'multer';
+import { ParseFlyerDto } from './dto/parse-flyer.dto';
+import { FlyerParseResponse, FlyerParsingService } from './flyer-parsing.service';
+
+const ALLOWED_UPLOAD_MIMES = new Set([
+  'application/pdf',
+  'application/octet-stream',
+  'text/plain',
+]);
+
+@Controller('flyer')
+export class FlyerParsingController {
+  constructor(private readonly flyerParsingService: FlyerParsingService) {}
+
+  @Post('parse')
+  @HttpCode(200)
+  @UseInterceptors(
+    FileInterceptor('file', {
+      storage: memoryStorage(),
+      limits: { fileSize: 15 * 1024 * 1024 },
+      fileFilter: (_req, file, cb) => {
+        if (ALLOWED_UPLOAD_MIMES.has(file.mimetype)) {
+          cb(null, true);
+          return;
+        }
+        cb(
+          new BadRequestException('Otillåten filtyp för flyer-parser. Stöd: PDF eller textfil.'),
+          false,
+        );
+      },
+    }),
+  )
+  async parseFlyer(
+    @Body() body: ParseFlyerDto,
+    @UploadedFile() file?: Express.Multer.File,
+  ): Promise<FlyerParseResponse> {
+    if (!file && !body?.text?.trim()) {
+      throw new BadRequestException('Skicka antingen fil under "file" eller text i body.text.');
+    }
+
+    const text = body?.text?.trim();
+    return this.flyerParsingService.parseFlyer({
+      file,
+      text,
+      retailer: body?.retailer ?? 'willys',
+    });
+  }
+}