Regroup the management event list to match the member app's agenda look

The desktop "List" view was a flat, paginated <table>. It's now grouped the
same way mobile.views.CalendarView already groups the member app's own
calendar: "This week" / "Next week", then everything further out under its
own month divider -- same algorithm (itertools.groupby over an already-
sorted, already-paginated page of events), applied after pagination so the
two don't fight each other. "Show past events" mode skips the this/next-week
labels (they only make sense for what's ahead) and just groups straight into
months, most recent first.

Each row keeps the same information and admin actions the table had (kind
badge, series icon, teams, location, Edit/Delete) -- just laid out as a list
row instead of table cells, in its own reusable partial.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

static/css/app.css

@@ -4423,9 +4423,18 @@
       margin-block-end: calc(calc(var(--spacing) * 2) * calc(1 - var(--tw-space-y-reverse)));
     }
   }
+  .gap-x-3 {
+    column-gap: calc(var(--spacing) * 3);
+  }
   .gap-x-4 {
     column-gap: calc(var(--spacing) * 4);
   }
+  .gap-y-0 {
+    row-gap: 0;
+  }
+  .gap-y-0\.5 {
+    row-gap: calc(var(--spacing) * 0.5);
+  }
   .gap-y-2 {
     row-gap: calc(var(--spacing) * 2);
   }
@@ -4813,6 +4822,9 @@
   .p-6 {
     padding: calc(var(--spacing) * 6);
   }
+  .p-8 {
+    padding: calc(var(--spacing) * 8);
+  }
   .p-10 {
     padding: calc(var(--spacing) * 10);
   }