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

@@ -281,7 +281,10 @@ 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 {
-		return c.JSON(http.StatusNotFound, map[string]string{"error": "user not found"})
+		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 := ""
@@ -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"})
 	}
 
@@ -738,11 +744,14 @@ 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 no settings found, return defaults
-		return c.JSON(http.StatusOK, map[string]interface{}{
-			"scan_frequency_minutes": 60,
-			"auto_scan_enabled":      true,
-		})
+		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{}{