settings: de-dupe settings

all DOM elements now based off DOMSetting, which encompasses most
functionality. Extending classes (i forgot the terminology) pretty much just pass a
custom "input" element, "hider" element (the one to unfocus). DOMList
and DOMSelect remain slightly more complicated, but are much cleaner
now. Some CSS stuff has been adjusted too.

config.go

@@ -127,6 +127,8 @@ func (app *appContext) loadConfig() error {
 	app.MustSetValue("user_expiry", "adjustment_email_html", "jfa-go:"+"expiry-adjusted.html")
 	app.MustSetValue("user_expiry", "adjustment_email_text", "jfa-go:"+"expiry-adjusted.txt")
 
+	app.MustSetValue("email", "collect", "true")
+
 	app.MustSetValue("matrix", "topic", "Jellyfin notifications")
 	app.MustSetValue("matrix", "show_on_reg", "true")