refactor: markup render (#38864) (#38869)

backport #38864

1. add missing CSP header to api & web render endpoints.
2. make jupyter render skip post-processors, nothing to process

routers/common/errpage.go

@@ -40,6 +40,7 @@ func renderServerErrorPage(w http.ResponseWriter, req *http.Request, respCode in
 	if acceptsHTML {
 		err := templates.PageRenderer().HTML(outBuf, respCode, tmpl, ctxData, tmplCtx)
 		if err != nil {
+			log.Error("Failed to render error page template %s: %v", tmpl, err)
 			_, _ = w.Write([]byte("Internal server error but failed to render error page template, please collect error logs and report to Gitea issue tracker"))
 			return
 		}

routers/common/markup.go

@@ -31,6 +31,8 @@ func RenderMarkup(ctx *context.Base, ctxRepo *context.Repository, mode, text, ur
 	// for example, when previewing file "/gitea/owner/repo/src/branch/features/feat-123/doc/CHANGE.md", then filePath is "doc/CHANGE.md"
 	// and the urlPathContext is "/gitea/owner/repo/src/branch/features/feat-123/doc"
 
+	ctx.SetHeaderContentSecurityPolicyGeneral()
+
 	if mode == "" || mode == "markdown" {
 		// raw Markdown doesn't do any special handling
 		// TODO: raw markdown doesn't do any link processing, so "urlPathContext" doesn't take effect