Improve error handling in auth handlers

- Add specific pgx.ErrNoRows checks in GetProfile
- Better error handling in UpdatePassword and GetScanSettings
- Return appropriate HTTP status codes for different error types
- Improve error message consistency

internal/handlers/auth.go

@@ -281,8 +281,11 @@ func (h *AuthHandler) GetProfile(c echo.Context) error {
 
 	user, err := h.db.GetUser(c.Request().Context(), pgtype.UUID{Bytes: userUUID, Valid: true})
 	if err != nil {
+		if err == pgx.ErrNoRows {
 			return c.JSON(http.StatusNotFound, map[string]string{"error": "user not found"})
 		}
+		return c.JSON(http.StatusInternalServerError, map[string]string{"error": err.Error()})
+	}
 
 	firstName := ""
 	if user.FirstName.Valid {
@@ -652,6 +655,9 @@ func (h *AuthHandler) UpdatePassword(c echo.Context) error {
 	// Get current user's password hash
 	passwordHash, err := h.db.GetUserPasswordHash(c.Request().Context(), pgtype.UUID{Bytes: userUUID, Valid: true})
 	if err != nil {
+		if err == pgx.ErrNoRows {
+			return c.JSON(http.StatusNotFound, map[string]string{"error": "user not found"})
+		}
 		return c.JSON(http.StatusInternalServerError, map[string]string{"error": "failed to get user"})
 	}
 
@@ -738,12 +744,15 @@ func (h *AuthHandler) GetScanSettings(c echo.Context) error {
 
 	settings, err := h.db.GetScanSettings(c.Request().Context(), pgtype.UUID{Bytes: userUUID, Valid: true})
 	if err != nil {
+		if err == pgx.ErrNoRows {
 			// If no settings found, return defaults
 			return c.JSON(http.StatusOK, map[string]interface{}{
 				"scan_frequency_minutes": 60,
 				"auto_scan_enabled":      true,
 			})
 		}
+		return c.JSON(http.StatusInternalServerError, map[string]string{"error": err.Error()})
+	}
 
 	return c.JSON(http.StatusOK, map[string]interface{}{
 		"scan_frequency_minutes": settings.ScanFrequencyMinutes.Int32,