Add boot splash; separate Systems Operational and Security icons

Loading indicator:
- Branded boot splash (Hub logo inside an accent spinner ring,
  "Starting The Hub") covers the shell while the first services
  data loads, then fades out once the welcome dashboard has
  rendered; never blocks longer than 25s and reassures the user
  after 8s (message about post-reboot delays)
- Fire the network and update checks before the first services
  render so the dashboard cards are current at first paint
- Sidebar Update button now adopts the last known update state
  when built (order-independent), and the welcome dashboard
  re-renders when the update state changes

Icons:
- New monochrome g-pulse glyph (activity line) for Systems
  Operational: welcome card, dialog header, and System Status
  section — the shield no longer doubles as Security
- Tech Support / Security dialog header gets a standard chip;
  Security shows the shield chip with a plain "Security" title
  (no emoji), and the shared dialog title now resets correctly
  when reopening Tech Support after Security

app/sovran_systemsos_web/static/js/dashboard.js

@@ -230,7 +230,7 @@
     var attentionTitle = c.attention ? "Systems need attention" : "Systems operational";
     $wcSystems.innerHTML =
       '<div class="widget clickable" id="w-systems" role="button" tabindex="0" title="System status and router setup">' +
-        '<div class="widget-chip chip-green">' + icon("g-shield-check") + '</div>' +
+        '<div class="widget-chip chip-green">' + icon("g-pulse") + '</div>' +
         '<div class="w-body"><h3>' + attentionTitle + '</h3><div class="sub">' + sub + '</div></div>' +
         '<span class="w-chev">' + icon("g-chev") + '</span>' +
       '</div>';
@@ -337,7 +337,7 @@
 
     /* System status */
     html += '<div class="sysmodal-card">' +
-      '<div class="sysmodal-card-title">' + icon("g-shield-check") + 'System Status</div>' +
+      '<div class="sysmodal-card-title">' + icon("g-pulse") + 'System Status</div>' +
       step(1, "Services running", "", String(c.running)) +
       step(2, "Needs attention", "", c.attention ? escHtml(c.attentionNames.join(", ")) : "None") +
       step(3, "Turned off", "", c.off ? escHtml(c.offNames.join(", ")) : "None") +