Add a season workload chart to the referee management dashboard

Games refereed per referee this season, as a chart.js bar chart plus a
small table with fees paid per referee, alongside season-at-a-glance KPIs
(active referees, total games refereed, average per referee) -- separate
from the existing "games in view" KPIs, which track the upcoming range
picked by the filter strip rather than season-to-date workload.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01ECGMEwrc2k4D8VQuwjstj9

static/css/app.css

@@ -4013,6 +4013,9 @@
   .h-screen {
     height: 100vh;
   }
+  .max-h-40 {
+    max-height: calc(var(--spacing) * 40);
+  }
   .max-h-60 {
     max-height: calc(var(--spacing) * 60);
   }
@@ -5682,6 +5685,11 @@
       line-height: var(--tw-leading, var(--text-4xl--line-height));
     }
   }
+  .lg\:col-span-2 {
+    @media (width >= 64rem) {
+      grid-column: span 2 / span 2;
+    }
+  }
   .lg\:flex {
     @media (width >= 64rem) {
       display: flex;