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/api/companies.ts

@@ -0,0 +1,14 @@
+import type { Company } from "@paperclip/shared";
+import { api } from "./client";
+
+export const companiesApi = {
+  list: () => api.get<Company[]>("/companies"),
+  get: (companyId: string) => api.get<Company>(`/companies/${companyId}`),
+  create: (data: { name: string; description?: string | null; budgetMonthlyCents?: number }) =>
+    api.post<Company>("/companies", data),
+  update: (
+    companyId: string,
+    data: Partial<Pick<Company, "name" | "description" | "status" | "budgetMonthlyCents">>,
+  ) => api.patch<Company>(`/companies/${companyId}`, data),
+  archive: (companyId: string) => api.post<Company>(`/companies/${companyId}/archive`, {}),
+};