style(web): update app styles and AppShellRouteView

- app.css: update app-level styles
- AppShellRouteView.vue: update app shell route view

web/src/assets/styles/app.css

@@ -18,7 +18,7 @@
   height: var(--desktop-stage-height, 100dvh);
   min-height: var(--desktop-stage-height, 100dvh);
   display: grid;
-  grid-template-columns: 220px minmax(0, 1fr);
+  grid-template-rows: auto auto minmax(0, 1fr);
   background: var(--bg);
 }
 
@@ -85,17 +85,10 @@
 
 .main { min-width: 0; min-height: 0; display: grid; grid-template-rows: auto auto minmax(0, 1fr); }
 .main.overview-main {
-  height: var(--desktop-stage-height, 100dvh);
   grid-template-rows: auto minmax(0, 1fr);
   overflow: hidden;
 }
 .main.workbench-main {
-  height: var(--desktop-stage-height, 100dvh);
-  grid-template-rows: auto minmax(0, 1fr);
-  overflow: hidden;
-}
-.main.chat-main {
-  height: var(--desktop-stage-height, 100dvh);
   grid-template-rows: auto minmax(0, 1fr);
   overflow: hidden;
 }
@@ -105,7 +98,6 @@
 .main.audit-main,
 .main.employees-main,
 .main.settings-main {
-  height: var(--desktop-stage-height, 100dvh);
   grid-template-rows: auto minmax(0, 1fr);
   overflow: hidden;
 }
@@ -116,10 +108,6 @@
   grid-template-rows: minmax(0, 1fr);
 }
 .workarea { min-height: 0; overflow: auto; padding: 24px; }
-.workarea.chat-workarea {
-  min-height: 0;
-  overflow: hidden;
-}
 .workarea.requests-workarea,
 .workarea.approval-workarea,
 .workarea.policies-workarea,
@@ -135,10 +123,10 @@
   background: #fff;
 }
 
-@media (max-width: 1180px) {
-  .app { grid-template-columns: 220px minmax(0, 1fr); }
-}
 @media (max-width: 760px) {
-  .app { display: block; }
+  .app {
+    height: auto;
+    min-height: 100dvh;
+  }
   .workarea { padding: 18px 16px 28px; }
 }