feat(helpdesk): redesign dashboards with KPI groups, skeleton loading, and unified spacing

Restructure Support dashboard into 2 KPI groups (Tickets + Contracts) with
section dividers, merge escalations and recommendations into "Attention needed".
Redesign Sales dashboard with clickable contract timeline and dialog.
Add CSS shimmer skeleton loading for all dashboard tabs and aside.
Unify vertical rhythm via * + * sibling combinator on tab content containers.
Remove ~265 lines of dead CSS (contract cards, escalation styles) and unused JS
functions. Refactor hydrateTicketCategoryFilter into generic hydrateSelectFilter.
Fix role="button" CSS bleed from shell and remove extra future year from timeline.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

web/css/layout/app-aside-icon-bar.css

@@ -16,6 +16,10 @@ aside.aside-icon-bar nav {
   height: 100vh;
 }
 
+aside.aside-icon-bar .aside-icon-footer {
+  display: grid;
+}
+
 aside.aside-icon-bar ul,
 aside.aside-icon-bar li {
   margin: 0;
@@ -94,6 +98,11 @@ aside.aside-icon-bar li button:focus-visible {
     gap: var(--app-spacing);
   }
 
+  aside.aside-icon-bar .aside-icon-footer {
+    display: flex;
+    gap: var(--app-spacing);
+  }
+
   aside.aside-icon-bar ul {
     display: flex;
     justify-content: space-around;

web/css/layout/app-sidebar.css

@@ -40,7 +40,7 @@
     display: inline-flex;
     align-items: center;
     justify-content: center;
-    font-size: 10px;
+    font-size: 10px; /* icon-font metric — intentional px */
     width: 1.45rem;
     height: 1.45rem;
     border-radius: 6px;