Migrate saju service UI

src/App.css

@@ -25,6 +25,16 @@
     margin-left: var(--sidebar-w);
 }
 
+.app-shell--immersive {
+    height: 100vh;
+    overflow: hidden;
+    background: #F7F2E8;
+}
+
+.app-content--immersive {
+    margin-left: 0;
+}
+
 /* ── Layout: Top Bar (mobile only) ──────────────────────────────────── */
 
 .app-topbar {
@@ -59,6 +69,11 @@
     position: relative;
 }
 
+.site-main--immersive {
+    padding: 0;
+    background: #F7F2E8;
+}
+
 @media (max-width: 768px) {
     .site-main {
         padding: 16px;
@@ -491,6 +506,17 @@
         overflow: visible;
         flex: none;
     }
+
+    .app-shell--immersive {
+        height: auto;
+        min-height: 100vh;
+        overflow: visible;
+    }
+
+    .site-main--immersive {
+        padding: 0;
+        padding-bottom: 0;
+    }
 }
 
 /* ── Accessibility: Reduced Motion ──────────────────────────────────── */