Fix Store tab stuck on Loading; adjustable idle time for family devices; videos count as in use

- A bare #/store now opens at #/store/books so the Book store page draws
- Admins choose how long a family device waits before returning to the board (1 to 30 minutes)
- Any playing video or audio keeps a family device signed in
- Test updated

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

public/store-view.js

@@ -15,6 +15,7 @@ const stSections = () => [['books', 'Books', allowed('read')], ['audiobooks', 'A
 
 async function viewStore(args = []) {
   const secs = stSections(), want = args[0] === 'ext' || args[0] === 'site' ? 'mine' : args[0], sec = (secs.find(s => s[0] === want) || secs[0])[0];
+  if (!args[0] || (!secs.some(s => s[0] === args[0]) && args[0] !== 'ext' && args[0] !== 'site')) return location.replace('#/store/' + sec); // (a bare #/store opens the first section by its own address, so its page knows it is the one showing)
   const v = $('#view');
   v.innerHTML = `<div class="wrap" id="stwrap"><div class="ptop"><h1>Store</h1></div><div class="seg">${secs.map(s => `<a href="#/store/${s[0]}" class="${s[0] === sec ? 'on' : ''}">${esc(s[1])}</a>`).join('')}</div><div id="stbody"></div></div>`;
   const el = $('#stbody'), host = { el, hash: '#/store/' + sec };