refactor: externalize AppPage component and streamline all tool pages

app/(app)/pastel/textcolor/page.tsx

@@ -5,6 +5,7 @@ import { ColorPicker } from '@/components/pastel/ColorPicker';
 import { ColorDisplay } from '@/components/pastel/ColorDisplay';
 import { Button } from '@/components/ui/button';
 import { Card, CardContent, CardHeader, CardTitle } from '@/components/ui/card';
+import { AppPage } from '@/components/layout/AppPage';
 import { useTextColor } from '@/lib/pastel/api/queries';
 import { Loader2, Palette, Plus, X, CheckCircle2, XCircle } from 'lucide-react';
 import { toast } from 'sonner';
@@ -55,16 +56,11 @@ export default function TextColorPage() {
   };
 
   return (
-    <div className="min-h-screen py-12">
-      <div className="max-w-7xl mx-auto px-8 space-y-8">
-        <div>
-          <h1 className="text-4xl font-bold mb-2">Text Color Optimizer</h1>
-          <p className="text-muted-foreground">
-            Automatically find the best text color (black or white) for any background color
-          </p>
-        </div>
-
-        <div className="grid grid-cols-1 lg:grid-cols-2 gap-8">
+    <AppPage
+      title="Text Color Optimizer"
+      description="Automatically find the best text color (black or white) for any background color"
+    >
+      <div className="grid grid-cols-1 lg:grid-cols-2 gap-8">
           {/* Input */}
           <div className="space-y-6">
             <Card>
@@ -226,7 +222,6 @@ export default function TextColorPage() {
             )}
           </div>
         </div>
-      </div>
-    </div>
+    </AppPage>
   );
 }