web: stop polling when the page has had no input for ten minutes

The firmware counts every authenticated request as session activity, and
the page polls the status every 2.5 s, so an open tab never let the
session expire. Track the last mouse, key, touch or wheel event and treat
the page as hidden once ten minutes have passed without one: the pollers
keep ticking but send nothing, the session times out in the firmware as
it did before, and the next input resumes polling, which meets the 401
and returns to the login page.

html/app.js

@@ -533,13 +533,18 @@ TABS.forEach(function(tb){
 });
 $("burger").addEventListener("click",function(){$("nav").classList.toggle("open")});
 
+var IDLE_STOP_MS=600000,lastInput=Date.now();
+["mousemove","mousedown","keydown","touchstart","wheel"].forEach(function(ev){
+  addEventListener(ev,function(){lastInput=Date.now()},{passive:true});
+});
 function Poller(fn,ms){this.fn=fn;this.ms=ms;this.on=false;this.t=null}
 Poller.prototype.start=function(){if(this.on)return;this.on=true;this.tick()};
 Poller.prototype.stop=function(){this.on=false;clearTimeout(this.t)};
 Poller.prototype.tick=function(){
   var self=this;
   if(!self.on)return;
-  var run=document.hidden?Promise.resolve():Promise.resolve().then(self.fn).catch(function(){});
+  var quiet=document.hidden||Date.now()-lastInput>IDLE_STOP_MS;
+  var run=quiet?Promise.resolve():Promise.resolve().then(self.fn).catch(function(){});
   run.then(function(){ if(self.on)self.t=setTimeout(function(){self.tick()},self.ms); });
 };