fix: surface DB error when team login refresh token issuance fails

Return err.Error() in the response so operators see e.g. missing
team_refresh_tokens table instead of a generic message.

Made-with: Cursor

internal/web_server/handlers/team_handler.go

@@ -153,7 +153,7 @@ func (h *Handler) TeamMemberLogin(c *fiber.Ctx) error {
 		)
 		return c.Status(fiber.StatusInternalServerError).JSON(domain.ErrorResponse{
 			Message: "Failed to login",
-			Error:   "Failed to issue refresh token",
+			Error:   err.Error(),
 		})
 	}