Fix wonky tables on dashboard and activity page

Tables with a `layout` of `fixed` determine column widths from the
width of the column headings.

We weren’t setting the width of the first column heading, so our tables
were getting out of alignment.

app/assets/stylesheets/components/table.scss

@@ -21,6 +21,10 @@
     }
   }
 
+  .table-field-heading-first {
+    width: 52.5%
+  }
+
   .table-row {
     th {
       display: table-cell;