Add admin-editable About page

Mirrors the existing Bio singleton pattern: a new `about` table/model,
admin CRUD at /admin/about, and a public page at /about linked from
both the header nav and the admin homepage. Content is wrapped in
.e-content so it lays out correctly within the site's CSS grid.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_013bzYwaDD8p3XNDMYKvXKrs

resources/views/admin/about/show.blade.php

@@ -0,0 +1,19 @@
+@extends('master')
+
+@section('title')Edit About « Admin CP « @stop
+
+@section('content')
+    <h1>Edit About</h1>
+    <form action="/admin/about" method="post" accept-charset="utf-8" class="admin-form form">
+        {{ csrf_field() }}
+        {{ method_field('PUT') }}
+        <div>
+            <label for="content">Content:</label>
+            <br>
+            <textarea name="content" id="content" rows="10" cols="50">{{ old('content', $aboutEntry?->content) }}</textarea>
+        </div>
+        <div>
+            <button type="submit" name="save">Save</button>
+        </div>
+    </form>
+@stop

resources/views/admin/welcome.blade.php

@@ -57,6 +57,11 @@
         Edit your <a href="/admin/bio">bio</a>.
     </p>
 
+    <h2>About</h2>
+    <p>
+        Edit your <a href="/admin/about">about page</a>.
+    </p>
+
     <h2>Passkeys</h2>
     <p>
         Manager <a href="/admin/passkeys">your passkeys</a>.