panel: stack Add an application above the list, drop the two-column row

The side-by-side .split row read badly: main is capped at 48rem, so the
applications table had to live in roughly 27rem and its actions column
squeezed four controls into it.

Put the create form directly above the list instead — the order the
domains page already uses for "Add a sending domain" above "Domains" —
and delete .split, which nothing else used. The empty-state text follows
the same page's wording.

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

internal/web/templates/domain_detail.html

@@ -144,11 +144,35 @@
   lost, generate a new one.</p>
 </div>
 
-{{/* Applications and its create form sit side by side on a wide viewport: the
-     table is read far more often than the form, and pairing them saves scrolling
-     past the list to add one. On a narrow viewport the .split grid stacks them
-     again, list first. */}}
-<div class="split">
+{{/* Create form above the list, the same order the domains page uses for
+     "Add a sending domain" above "Domains". */}}
+<div class="card">
+  <h2>Add an application</h2>
+  <form method="post" action="/domains/{{.Domain.ID}}/applications">
+    <label for="login">Login</label>
+    <input id="login" name="login" type="text" placeholder="prod-server"
+           autocomplete="off" autocapitalize="none" spellcheck="false"
+           value="{{.FormLogin}}" required>
+
+    <label for="mode">Address mode</label>
+    <select id="mode" name="mode" data-list-mode="{{.List}}">
+      <option value="{{.Wildcard}}" {{if eq .FormMode .Wildcard}}selected{{end}}>Any address of the domain</option>
+      <option value="{{.List}}" {{if eq .FormMode .List}}selected{{end}}>Specific addresses (list)</option>
+    </select>
+
+    <div data-addresses>
+      <label for="addresses">Addresses (one per line or comma-separated)</label>
+      <textarea id="addresses" name="addresses" rows="3"
+                placeholder="alerts@{{.Domain.Name}}">{{.FormAddrs}}</textarea>
+    </div>
+
+    {{if .Error}}<p class="error">{{.Error}}</p>{{end}}
+    <button type="submit">Create application</button>
+  </form>
+  <p class="muted">A strong password is generated and shown once. The login must
+  be unique across all domains and may contain letters, digits, '.', '-' and '_'.</p>
+</div>
+
 <div class="card">
   <h2>Applications</h2>
   <p class="muted">Each application is a SASL login/password an app or script
@@ -220,39 +244,10 @@
     </tbody>
   </table>
   {{else}}
-  <p class="muted">No applications yet. Create the first one with the
-  <strong>Add an application</strong> form.</p>
+  <p class="muted">No applications yet. Add one above to get started.</p>
   {{end}}
 </div>
 
-<div class="card">
-  <h2>Add an application</h2>
-  <form method="post" action="/domains/{{.Domain.ID}}/applications">
-    <label for="login">Login</label>
-    <input id="login" name="login" type="text" placeholder="prod-server"
-           autocomplete="off" autocapitalize="none" spellcheck="false"
-           value="{{.FormLogin}}" required>
-
-    <label for="mode">Address mode</label>
-    <select id="mode" name="mode" data-list-mode="{{.List}}">
-      <option value="{{.Wildcard}}" {{if eq .FormMode .Wildcard}}selected{{end}}>Any address of the domain</option>
-      <option value="{{.List}}" {{if eq .FormMode .List}}selected{{end}}>Specific addresses (list)</option>
-    </select>
-
-    <div data-addresses>
-      <label for="addresses">Addresses (one per line or comma-separated)</label>
-      <textarea id="addresses" name="addresses" rows="3"
-                placeholder="alerts@{{.Domain.Name}}">{{.FormAddrs}}</textarea>
-    </div>
-
-    {{if .Error}}<p class="error">{{.Error}}</p>{{end}}
-    <button type="submit">Create application</button>
-  </form>
-  <p class="muted">A strong password is generated and shown once. The login must
-  be unique across all domains and may contain letters, digits, '.', '-' and '_'.</p>
-</div>
-</div>
-
 <div class="card">
   <h2>Sending rate limit (domain)</h2>
   <p class="muted">Optional level-2 limit (spec 7.4): cap how many messages this