feat: add sidebar collapse, category/tag filtering, and workspace CRUD (Phase D)

- Sidebar collapse/expand toggle with icon-only rail mode (persisted)
- Sidebar category/tag clicks navigate to /trees with URL params
- TreeLibraryPage syncs filters from URL search params bidirectionally
- Workspace create modal with icon picker and auto-slug generation
- TopBar logo adapts to collapsed sidebar state

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

frontend/src/components/layout/TopBar.tsx

@@ -14,6 +14,7 @@ export function TopBar() {
   const { user, logout } = useAuthStore()
   const { effectiveRole, isSuperAdmin } = usePermissions()
   const activeWorkspace = useWorkspaceStore(s => s.getActiveWorkspace())
+  const sidebarCollapsed = useWorkspaceStore(s => s.sidebarCollapsed)
   const labels = getWorkspaceLabels(activeWorkspace?.slug)
 
   const [userMenuOpen, setUserMenuOpen] = useState(false)
@@ -57,14 +58,20 @@ export function TopBar() {
     <>
       <header className="topbar flex items-center gap-4 border-b border-border bg-background px-4">
         {/* Logo area */}
-        <Link to="/" className="flex items-center gap-2.5 pr-4" style={{ width: 'calc(260px - 40px)' }}>
-          <div className="flex h-8 w-8 items-center justify-center rounded-lg bg-gradient-brand">
+        <Link
+          to="/"
+          className="flex items-center gap-2.5 pr-4 transition-all duration-200"
+          style={{ width: sidebarCollapsed ? '32px' : 'calc(260px - 40px)' }}
+        >
+          <div className="flex h-8 w-8 shrink-0 items-center justify-center rounded-lg bg-gradient-brand">
             <BrandLogo size="sm" className="h-4 w-4" />
           </div>
-          <span className="text-sm font-heading font-bold tracking-tight">
-            <span className="text-foreground">Resolution</span>
-            <span className="text-gradient-brand">Flow</span>
-          </span>
+          {!sidebarCollapsed && (
+            <span className="text-sm font-heading font-bold tracking-tight">
+              <span className="text-foreground">Resolution</span>
+              <span className="text-gradient-brand">Flow</span>
+            </span>
+          )}
         </Link>
 
         {/* Search trigger */}