[FIX] Register: Améliorer logs d'erreur pour diagnostic

- Ajouter logs détaillés dans service.go (erreur PostgreSQL complète)
- Ajouter logs détaillés dans handler (erreur complète avant encapsulation)
- Capturer type d'erreur, message, et contexte
- Gérer erreurs CHECK constraint, ENUM manquant, timeout
- Permettre identification précise de l'erreur réelle

veza-backend-api/internal/core/auth/service.go

@@ -230,14 +230,23 @@ func (s *AuthService) Register(ctx context.Context, email, username, password st
 		fmt.Printf("========== REGISTER: DB INSERT ERROR ==========\n")
 		fmt.Printf(">>> ERROR: %v\n", result.Error)
 		fmt.Printf(">>> ERROR TYPE: %T\n", result.Error)
+		fmt.Printf(">>> ERROR STRING: %s\n", result.Error.Error())
 		fmt.Printf(">>> ROWS AFFECTED: %d\n", result.RowsAffected)
 		fmt.Printf("===============================================\n")
+		
 		// Log l'erreur complète pour diagnostic
 		err := result.Error
-		s.logger.Error("Failed to create user in database - full error details",
+		errMsg := err.Error()
+		errType := fmt.Sprintf("%T", err)
+		
+		s.logger.Error("Failed to create user in database - FULL ERROR DETAILS",
 			zap.Error(err),
+			zap.String("error_type", errType),
+			zap.String("error_string", errMsg),
 			zap.String("email", email),
 			zap.String("username", username),
+			zap.String("slug", slug),
+			zap.String("role", user.Role),
 			zap.String("user_id", user.ID.String()),
 			zap.Any("user_fields", map[string]interface{}{
 				"is_banned":     user.IsBanned,
@@ -250,22 +259,46 @@ func (s *AuthService) Register(ctx context.Context, email, username, password st
 			}),
 		)
 
+		// Vérifier les erreurs PostgreSQL spécifiques
+		// Contrainte CHECK
+		if strings.Contains(errMsg, "violates check constraint") {
+			if strings.Contains(errMsg, "chk_users_username_format") {
+				s.logger.Warn("Registration failed: username format invalid", zap.String("username", username))
+				return nil, nil, errors.New("username format invalid: must be 3-30 alphanumeric characters")
+			}
+			if strings.Contains(errMsg, "chk_users_email_format") {
+				s.logger.Warn("Registration failed: email format invalid", zap.String("email", email))
+				return nil, nil, errors.New("email format invalid")
+			}
+			// Autre contrainte CHECK
+			s.logger.Warn("Registration failed: check constraint violation", zap.Error(err))
+			return nil, nil, fmt.Errorf("validation failed: %w", err)
+		}
+		
+		// Type ENUM manquant
+		if strings.Contains(errMsg, "does not exist") && strings.Contains(errMsg, "user_role") {
+			s.logger.Error("Registration failed: user_role enum missing from database")
+			return nil, nil, fmt.Errorf("database schema error: user_role enum missing - run migrations")
+		}
+		
+		// Timeout
+		if strings.Contains(errMsg, "context deadline exceeded") || strings.Contains(errMsg, "timeout") {
+			s.logger.Warn("Registration failed: database operation timed out")
+			return nil, nil, fmt.Errorf("database operation timed out: %w", err)
+		}
+		
 		// PostgreSQL error code 23505 is unique_violation
 		// We check for specific constraint names if possible, or fallback to generic "duplicate"
-		errMsg := err.Error()
 		if strings.Contains(errMsg, "users_email_key") || strings.Contains(errMsg, "idx_users_email") {
 			s.logger.Warn("Registration failed: email already exists", zap.String("email", email))
 			return nil, nil, services.ErrUserAlreadyExists
 		}
 		if strings.Contains(errMsg, "users_username_key") || strings.Contains(errMsg, "idx_users_username") {
 			s.logger.Warn("Registration failed: username already exists", zap.String("username", username))
-			// We can return the same error or a more specific one if needed
 			return nil, nil, errors.New("username already exists")
 		}
 		if strings.Contains(errMsg, "users_slug_key") || strings.Contains(errMsg, "idx_users_slug") {
 			s.logger.Warn("Registration failed: slug collision", zap.String("slug", user.Slug))
-			// In a real robust system, we would retry with a suffix here
-			// For now, fail explicitly so the user knows
 			return nil, nil, errors.New("username unavailable (slug collision)")
 		}
 
@@ -276,7 +309,13 @@ func (s *AuthService) Register(ctx context.Context, email, username, password st
 		}
 
 		// Pour toutes les autres erreurs, retourner l'erreur originale avec contexte
-		return nil, nil, fmt.Errorf("database error: %w", err)
+		// IMPORTANT: Inclure l'erreur complète pour diagnostic
+		s.logger.Error("Registration failed: unknown database error", 
+			zap.Error(err),
+			zap.String("error_type", errType),
+			zap.String("error_string", errMsg),
+		)
+		return nil, nil, fmt.Errorf("database error [%s]: %w", errType, err)
 	}
 	
 	fmt.Printf("========== REGISTER: DB INSERT SUCCESS ==========\n")

veza-backend-api/internal/handlers/auth.go

@@ -175,7 +175,14 @@ func Register(authService *auth.AuthService, sessionService *services.SessionSer
 			case services.IsWeakPassword(err):
 				RespondWithAppError(c, apperrors.NewValidationError("Password does not meet requirements"))
 			default:
-				commonHandler.logger.Error("Registration failed", zap.Error(err))
+				// Log l'erreur complète pour diagnostic
+				commonHandler.logger.Error("Registration failed - FULL ERROR",
+					zap.Error(err),
+					zap.String("error_type", fmt.Sprintf("%T", err)),
+					zap.String("error_string", err.Error()),
+					zap.String("email", req.Email),
+					zap.String("username", req.Username),
+				)
 				RespondWithAppError(c, apperrors.Wrap(apperrors.ErrCodeInternal, "Failed to create user", err))
 			}
 			return