Accounts: Unlink Telegram/Discord/Matrix through cog

Added an unlinking section to the little cog dropdown next to users so
that one can remove and re-link a different account for a Jellyfin user.
Also adjusted padding in the dropdown.

router.go

@@ -192,6 +192,9 @@ func (app *appContext) loadRoutes(router *gin.Engine) {
 			api.GET(p+"/telegram/pin", app.TelegramGetPin)
 			api.GET(p+"/telegram/verified/:pin", app.TelegramVerified)
 			api.POST(p+"/users/telegram", app.TelegramAddUser)
+			api.DELETE(p+"/users/telegram", app.UnlinkTelegram)
+			api.DELETE(p+"/users/discord", app.UnlinkDiscord)
+			api.DELETE(p+"/users/matrix", app.UnlinkMatrix)
 		}
 		if emailEnabled {
 			api.POST(p+"/users/contact", app.SetContactMethods)