Feat: Add responsive workspace shell

Frontend/src/components/shell/AppShell/AppShell.module.scss

@@ -8,8 +8,10 @@
 }
 
 .body {
+  --shell-dock-clearance: calc(var(--space-12) + var(--space-12) + var(--space-8));
   --rail-width: 4.75rem;
   --sidebar-width: 16.75rem;
+  --mobile-bottom-nav-clearance: 0rem;
   --shell-top-left-radius: calc(var(--radius-xl) + var(--space-1));
   --shell-frame-border: color-mix(in srgb, var(--color-border-strong) 44%, transparent);
   --shell-divider-border: color-mix(in srgb, var(--color-border-strong) 34%, transparent);
@@ -101,6 +103,16 @@
   border-top-right-radius: 0;
 }
 
+.mobileWorkspaceView {
+  min-width: 0;
+  min-height: 0;
+  height: 100%;
+  display: grid;
+  box-sizing: border-box;
+  overflow: hidden;
+  background: var(--workspace-panel-surface);
+}
+
 .sidebarDock {
   position: absolute;
   bottom: var(--space-3);
@@ -191,17 +203,46 @@
 
 @include respond-down(mobile) {
   .body {
-    grid-template-columns: 4.5rem minmax(0, 1fr);
-    --rail-width: 4.5rem;
+    grid-template-columns: minmax(0, 1fr);
+    --rail-width: 0rem;
+    --sidebar-width: 0rem;
+    --mobile-bottom-nav-clearance: calc(var(--space-12) + var(--space-10) + env(safe-area-inset-bottom, 0px));
   }
 
   .railColumn {
-    position: sticky;
-    top: 0;
+    display: none;
   }
 
-  .workspaceRegion,
+  .workspaceRegion {
+    display: grid;
+    grid-template-columns: minmax(0, 1fr);
+    border-top-left-radius: 0;
+  }
+
+  .workspaceRegion::before {
+    background: var(--workspace-panel-surface);
+    border-left-width: 0;
+    border-right-width: 0;
+    border-top-left-radius: 0;
+  }
+
+  .sidebarColumn,
   .sidebarDock {
     display: none;
   }
+
+  .workspaceMain {
+    border-left-width: 0;
+    border-top-right-radius: 0;
+    border-top-left-radius: 0;
+    box-sizing: border-box;
+    padding-bottom: var(--mobile-bottom-nav-clearance);
+  }
+
+  .mobileWorkspaceView {
+    height: 100%;
+    max-height: none;
+    padding-bottom: 0;
+    background: var(--workspace-panel-surface);
+  }
 }