Add integration tests for API routes

[Copilot]

Adds comprehensive integration test coverage for all API route handlers using Vitest and supertest against in-memory SQLite databases.

Tests Added

• 7 new route test files: supplier, headquarters, product, order, orderDetail, delivery, orderDetailDelivery
• 46 new tests covering CRUD operations, error cases, and foreign key relationships
• 64 total tests passing (18 existing + 46 new)

Repository Bug Fix

Fixed singleton caching issue in 4 repository getter functions that prevented proper test isolation:

• getHeadquartersRepository
• getProductsRepository
• getOrderDetailsRepository
• getOrderDetailDeliveriesRepository

These repositories cached database connections across tests. Added test environment detection to return fresh instances:

export async function getHeadquartersRepository(isTest: boolean = false): Promise<HeadquartersRepository> {
  const isTestEnv = isTest || process.env.NODE_ENV === 'test' || process.env.VITEST === 'true';
  if (isTestEnv) {
    return createHeadquartersRepository(true);  // Fresh instance per test
  }
  // Singleton for production
  if (!headquartersRepo) {
    headquartersRepo = await createHeadquartersRepository(false);
  }
  return headquartersRepo;
}

Pattern already existed in branchesRepo, suppliersRepo, ordersRepo, and deliveriesRepo but was missing in the above four.

Coverage

• Routes: 70.94% statement coverage, 100% function coverage
• All tests follow established pattern: fresh DB per test, proper foreign key seeding, supertest for HTTP assertions

Original prompt

create tests for api layer

The user has attached the following file paths as relevant context:

• .github\copilot-instructions.md

Created from VS Code.

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