fix(handlers): use http.ServeFile for better static file serving

Replace echo's c.File() with standard library http.ServeFile() in the
ServeFile handler. This provides more reliable static file serving and
better handles edge cases in file delivery.

internal/handlers/media.go

@@ -1549,5 +1549,6 @@ func (mh *MediaHandler) ServeFile(c *echo.Context) error {
 
 	c.Response().Header().Set("Content-Type", contentType)
 	c.Response().Header().Set("Cache-Control", "public, max-age=86400")
-	return c.File(fullPath)
+	http.ServeFile(c.Response(), c.Request(), fullPath)
+	return nil
 }