Toggle tasks and edit view settings via htmx

Task checkboxes post themselves (hx-post="?toggle=N") and flip back when
the save fails, replacing tasks.js. View settings are a server-rendered
form dialog with real radios and a select, replacing view-settings.js;
with that, postReplace has no callers left.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

pagesettings.go

@@ -23,7 +23,7 @@ func (h *handler) handleSettings(w http.ResponseWriter, r *http.Request, urlPath
 		http.Error(w, "write failed: "+err.Error(), http.StatusInternalServerError)
 		return
 	}
-	http.Redirect(w, r, urlPath, http.StatusSeeOther)
+	redirectAfter(w, r, pageURL(urlPath))
 }
 
 // writePageSettings performs a read-modify-write of <dir>/.page-settings,