Overhaul UI with shadcn components and new pages

Add shadcn/ui components (badge, button, card, input, select,
separator). Add company context provider. New pages: Activity,
Approvals, Companies, Costs, Org chart. Restyle existing pages
(Dashboard, Agents, Issues, Goals, Projects) with shadcn components
and dark theme. Update layout, sidebar navigation, and routing.

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

ui/src/components/Sidebar.tsx

@@ -3,15 +3,20 @@ import { cn } from "../lib/utils";
 
 const links = [
   { to: "/", label: "Dashboard" },
+  { to: "/companies", label: "Companies" },
+  { to: "/org", label: "Org" },
   { to: "/agents", label: "Agents" },
+  { to: "/tasks", label: "Tasks" },
   { to: "/projects", label: "Projects" },
-  { to: "/issues", label: "Issues" },
   { to: "/goals", label: "Goals" },
+  { to: "/approvals", label: "Approvals" },
+  { to: "/costs", label: "Costs" },
+  { to: "/activity", label: "Activity" },
 ];
 
 export function Sidebar() {
   return (
-    <aside className="w-56 border-r border-gray-200 bg-white p-4 flex flex-col gap-1">
+    <aside className="w-56 border-r border-border bg-card p-4 flex flex-col gap-1">
       <h1 className="text-lg font-bold mb-6 px-3">Paperclip</h1>
       <nav className="flex flex-col gap-1">
         {links.map((link) => (
@@ -23,8 +28,8 @@ export function Sidebar() {
               cn(
                 "px-3 py-2 rounded-md text-sm font-medium transition-colors",
                 isActive
-                  ? "bg-gray-100 text-gray-900"
-                  : "text-gray-600 hover:bg-gray-50 hover:text-gray-900"
+                  ? "bg-accent text-accent-foreground"
+                  : "text-muted-foreground hover:bg-accent/50 hover:text-accent-foreground"
               )
             }
           >