Add page management to the structured editor

Pages can now be reordered, renamed, and have their metadata edited
without touching YAML.

- Up/down arrows next to each page in the /edit list to reorder.
- "Settings" button per page opens /edit/pages/{slug}/settings — a
  form covering name, slug, page width, desktop nav width, mobile
  header, hide desktop nav, center vertically.
- POST /edit/api/pages/{slug}/fields applies metadata changes
  surgically via the existing yaml.Node + atomic-save flow so
  columns/widgets/comments stay untouched.
- POST /edit/api/pages/{slug}/move?dir=up|down swaps adjacent pages.

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

internal/glance/templates/admin.html

@@ -21,6 +21,15 @@
                     <span class="color-subdue"> — {{ .WidgetCount }} widget{{ if ne .WidgetCount 1 }}s{{ end }}</span>
                     <div class="color-subdue size-h5">/{{ .Slug }}</div>
                 </div>
+                <form method="post" action="{{ $.App.Config.Server.BaseURL }}/edit/api/pages/{{ .Slug }}/move?dir=up">
+                    <button type="submit" {{ if .IsFirst }}disabled{{ end }} title="Move up">↑</button>
+                </form>
+                <form method="post" action="{{ $.App.Config.Server.BaseURL }}/edit/api/pages/{{ .Slug }}/move?dir=down">
+                    <button type="submit" {{ if .IsLast }}disabled{{ end }} title="Move down">↓</button>
+                </form>
+                <a href="{{ $.App.Config.Server.BaseURL }}/edit/pages/{{ .Slug }}/settings" title="Page settings">
+                    <button type="button">Settings</button>
+                </a>
                 <form method="post" action="{{ $.App.Config.Server.BaseURL }}/edit/api/pages/{{ .Slug }}/delete"
                       onsubmit="return confirm('Delete page &quot;{{ .Title }}&quot; and all its widgets?');">
                     <button type="submit" class="color-negative">Delete</button>