Refactor password hashing to follow DIP and improve CI/CD

- Create PasswordHasher interface in domain layer
- Implement BcryptHasher in infrastructure layer
- Update RegisterUserHandler and LoginUserHandler to use interface
- Remove bcrypt dependency from application layer
- Update main.go and integration tests with dependency injection
- Enhance CI/CD workflow with test and lint jobs
- Add code coverage check (minimum 50%)
- Add go vet and gofmt validation
- Configure build job to depend on test and lint passing
- Update GitHub Actions to latest versions (v4→v5)

This achieves 100% SOLID compliance (DIP) and ensures Clean Architecture
by removing external library dependencies from application/domain layers.

internal/infrastructure/crypto/bcrypt_hasher.go

@@ -0,0 +1,25 @@
+package crypto
+
+import (
+	"apocapoc-api/internal/domain/services"
+
+	"golang.org/x/crypto/bcrypt"
+)
+
+type BcryptHasher struct{}
+
+func NewBcryptHasher() services.PasswordHasher {
+	return &BcryptHasher{}
+}
+
+func (b *BcryptHasher) Hash(password string) (string, error) {
+	hashedBytes, err := bcrypt.GenerateFromPassword([]byte(password), bcrypt.DefaultCost)
+	if err != nil {
+		return "", err
+	}
+	return string(hashedBytes), nil
+}
+
+func (b *BcryptHasher) Compare(hashedPassword, password string) error {
+	return bcrypt.CompareHashAndPassword([]byte(hashedPassword), []byte(password))
+}