style: refactor layout and enhance card UI in WeeklyManager

- Updated `WeeklyManagerPage` layout to use a `<main>` tag for better semantic structure.
- Refined `ManagerWeeklySummary` component to display narrative and metrics side by side, improving visual organization.
- Enhanced `AchievementCard` and `ChallengeCard` styles for better color differentiation and user experience.
- Adjusted spacing and grid layouts for improved responsiveness and clarity in the UI.

src/app/weekly-manager/page.tsx

@@ -19,15 +19,13 @@ export default async function WeeklyManagerPage() {
     <div className="min-h-screen bg-[var(--background)]">
       <Header />
       
-      <div className="container mx-auto px-4 py-8">
-        <div className="max-w-6xl mx-auto">
-          <WeeklyManagerPageClient 
-            initialSummary={summary}
-            initialTasks={initialTasks}
-            initialTags={initialTags}
-          />
-        </div>
-      </div>
+      <main className="container mx-auto px-6 py-8">
+        <WeeklyManagerPageClient 
+          initialSummary={summary}
+          initialTasks={initialTasks}
+          initialTags={initialTags}
+        />
+      </main>
     </div>
   );
 }