feat: implement Focus Mode (Speed Read) with swipeable card deck

web/src/layouts/RootLayout.tsx

@@ -1,19 +1,28 @@
 import { useState } from 'react';
 import { Sidebar } from '../components/Sidebar';
 import { DashboardPage } from '../pages/DashboardPage';
+import { FocusPage } from '../pages/FocusPage';
 
 export function RootLayout() {
     const [selectedFeedId, setSelectedFeedId] = useState<string | null>(null);
+    const [isFocusMode, setIsFocusMode] = useState(false);
 
     return (
         <div className="flex h-screen bg-carbon overflow-hidden">
             <Sidebar
                 onSelectFeed={setSelectedFeedId}
                 selectedFeedId={selectedFeedId}
+                onEnterFocus={() => setIsFocusMode(true)}
+                isFocusMode={isFocusMode}
             />
-            <DashboardPage
-                selectedFeedId={selectedFeedId}
-            />
+            {isFocusMode ? (
+                <FocusPage onExit={() => setIsFocusMode(false)} />
+            ) : (
+                <DashboardPage
+                    selectedFeedId={selectedFeedId}
+                    onEnterFocus={() => setIsFocusMode(true)}
+                />
+            )}
         </div>
     );
 }