refactor: externalize AppPage component and streamline all tool pages

app/(app)/pastel/page.tsx

@@ -7,6 +7,7 @@ import { ColorDisplay } from '@/components/pastel/ColorDisplay';
 import { ColorInfo } from '@/components/pastel/ColorInfo';
 import { ManipulationPanel } from '@/components/pastel/ManipulationPanel';
 import { Card, CardContent, CardHeader, CardTitle } from '@/components/ui/card';
+import { AppPage } from '@/components/layout/AppPage';
 import { useColorInfo } from '@/lib/pastel/api/queries';
 import { useColorHistory } from '@/lib/pastel/stores/historyStore';
 import { Loader2, Share2, History, X } from 'lucide-react';
@@ -73,16 +74,11 @@ function PlaygroundContent() {
   };
 
   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">Pastel</h1>
-          <p className="text-muted-foreground">
-            Interactive color manipulation and analysis tool
-          </p>
-        </div>
-
-        <div className="grid grid-cols-1 lg:grid-cols-2 gap-8">
+    <AppPage
+      title="Pastel"
+      description="Interactive color manipulation and analysis tool"
+    >
+      <div className="grid grid-cols-1 lg:grid-cols-2 gap-8">
           {/* Left Column: Color Picker and Display */}
           <div className="space-y-6">
             <Card>
@@ -197,8 +193,7 @@ function PlaygroundContent() {
             </Card>
           </div>
         </div>
-      </div>
-    </div>
+    </AppPage>
   );
 }