panel: give the monitoring pages a width that fits their data

48rem is a reading measure, right for the panel's forms and prose and the width
the nav bar's two rows were sized for. Deliveries, Mail queue and System log
hold data instead: seven columns of send-log, and mail.log lines that are long
by nature. They get 64rem; every other page keeps the narrow measure. The page
name travels onto <main> as a class so the stylesheet can tell them apart
without every handler having to pass a second field.

Width alone does not make a table fit, though — a column is at least as wide as
the longest unbreakable run in it, and one 40-character recipient still hung
Status over the card's edge. Cells may now break mid word, with timestamps
exempt, so a column can always be squeezed into the room available.

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

internal/web/templates/deliveries_rows.html

@@ -9,7 +9,7 @@
     <tbody>
       {{range .Rows}}
       <tr>
-        <td class="muted">{{.CreatedAt.Format "2006-01-02 15:04:05"}}</td>
+        <td class="time muted">{{.CreatedAt.Format "2006-01-02 15:04:05"}}</td>
         <td>{{.Domain}}</td>
         <td>{{.AppLogin}}</td>
         <td>{{.From}}</td>