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

database/migrations/2026_08_28_142830_create_about_table.php

@@ -0,0 +1,28 @@
+<?php
+
+use Illuminate\Database\Migrations\Migration;
+use Illuminate\Database\Schema\Blueprint;
+use Illuminate\Support\Facades\Schema;
+
+return new class extends Migration
+{
+    /**
+     * Run the migrations.
+     */
+    public function up(): void
+    {
+        Schema::create('about', function (Blueprint $table) {
+            $table->id();
+            $table->text('content');
+            $table->timestamps();
+        });
+    }
+
+    /**
+     * Reverse the migrations.
+     */
+    public function down(): void
+    {
+        Schema::dropIfExists('about');
+    }
+};