feat(helpdesk): add team workload dashboard with per-agent metrics

New standalone page (helpdesk/team) showing support agent workload
aggregated from BC tickets. KPI bar (open, unassigned, avg age, resolved),
per-agent table sorted by open tickets, period selector (30/90/180/365d).
Global OData query via getTicketsForTeam() without customer filter.
New permission helpdesk.team-workload.view with admin role assignment.
Includes 6 PHPUnit tests for buildTeamWorkloadDashboard().

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

modules/helpdesk/web/css/helpdesk.css

@@ -126,6 +126,50 @@
     }
   }
 
+  /* Team workload dashboard */
+  .helpdesk-team-period-selector {
+    display: inline-flex;
+    gap: calc(var(--app-spacing) * 0.25);
+    margin-bottom: calc(var(--app-spacing) * 0.75);
+  }
+
+  .helpdesk-team-period-button {
+    padding: calc(var(--app-spacing) * 0.25) calc(var(--app-spacing) * 0.6);
+    font-size: var(--text-sm, 0.875rem);
+    border: var(--app-border-width) solid var(--app-muted-border-color);
+    background: var(--app-background-color);
+    color: var(--app-color);
+    cursor: pointer;
+    transition: background-color 0.15s ease, border-color 0.15s ease;
+  }
+
+  .helpdesk-team-period-button.active {
+    background: var(--app-primary);
+    border-color: var(--app-primary);
+    color: var(--app-primary-inverse);
+  }
+
+  .helpdesk-team-table {
+    width: 100%;
+    margin-top: calc(var(--app-spacing) * 0.75);
+  }
+
+  .helpdesk-team-table th,
+  .helpdesk-team-table td {
+    text-align: left;
+    padding: calc(var(--app-spacing) * 0.35) calc(var(--app-spacing) * 0.5);
+  }
+
+  .helpdesk-team-table th:not(:first-child),
+  .helpdesk-team-table td:not(:first-child) {
+    text-align: right;
+  }
+
+  .helpdesk-team-row-unassigned {
+    opacity: 0.7;
+    font-style: italic;
+  }
+
   /* Clickable rows — shared between search results and ticket list */
   .app-clickable-row {
     cursor: pointer;