fix: never return frontend on routes starting with /api

This fixes a problem where Vikunja would sometimes return the html for the frontend when accessing an api route for a nonexistent ressource, because the static handler was the next best.

Resolves vikunja/vikunja#2110

pkg/routes/static.go

@@ -141,6 +141,9 @@ func static() echo.MiddlewareFunc {
 	return func(next echo.HandlerFunc) echo.HandlerFunc {
 		return func(c echo.Context) (err error) {
 			p := c.Request().URL.Path
+			if strings.HasPrefix(p, "/api/") {
+				return next(c)
+			}
 			if strings.HasSuffix(c.Path(), "*") { // When serving from a group, e.g. `/static*`.
 				p = c.Param("*")
 			}