chore(import): improve error handling and add flyer integration

- Replace BadRequestException with UnauthorizedException for authentication failures in flyer-import and flyer-selection controllers
- Add bulk selection endpoint in FlyerSelectionController for creating multiple selections in one request
- Update FlyerSelectionModule to include new FlyerSelectionMatcherService and FlyerSelectionSyncController
- Extend FlyerSelectionService with createMany method for bulk operations
- Add new DTOs for bulk selection and receipt matching functionality
- Update ReceiptImportService to accept FlyerSelectionService dependency and track successful rows
- Extend SaveReceiptResponse with flyerAutoSync field for receipt-to-flyer matching results
- Add new API paths for flyer import and selection endpoints
- Update Flutter UI to include Flyer import tab and adjust tab controller length
- Add new domain models and repository methods for flyer import functionality
- Update test files to include new FlyerSelectionService dependency
- Modify .kilo plan documentation to reflect current system architecture

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

@@ -6,9 +6,10 @@ import {
   Request,
   UploadedFile,
   UseGuards,
-  UseInterceptors,
-  BadRequestException,
-} from '@nestjs/common';
+  UseInterceptors,
+  BadRequestException,
+  UnauthorizedException,
+} from '@nestjs/common';
 import { Throttle } from '@nestjs/throttler';
 import { FileInterceptor } from '@nestjs/platform-express';
 import { memoryStorage } from 'multer';
@@ -72,7 +73,7 @@ export class ReceiptImportController {
           ? req.user.userId
           : undefined;
     if (!userId) {
-      throw new BadRequestException('Kunde inte identifiera användaren.');
+      throw new UnauthorizedException('Kunde inte identifiera användaren.');
     }
 
     return this.receiptImportService.upsertUnitMapping(
@@ -98,7 +99,7 @@ export class ReceiptImportController {
           ? req.user.userId
           : undefined;
     if (!userId) {
-      throw new BadRequestException('Kunde inte identifiera användaren.');
+      throw new UnauthorizedException('Kunde inte identifiera användaren.');
     }
 
     const isAdmin = req?.user?.role === 'admin';