fix: resolve majority of lint errors across codebase

- Remove unused imports from page.tsx, clients/page.tsx, invoices/page.tsx
- Remove unused imports from invoice-form.tsx, invoice-workspace.tsx
- Move CustomTooltip outside component in revenue-chart.tsx (fixes react-hooks/static-components)
- Fix type safety in umami.ts (any -> unknown)
- Fix type safety in sidebar-provider.tsx (add type assertion)
- Add no-op comments to empty fallback functions in animation-preferences-provider.tsx
- Fix type safety in invoice-workspace.tsx (any[] -> typed array)

Note: dashboard/page.tsx still has ~55 type safety warnings related to 'any' types
in stats/invoice data. These are pre-existing and would require significant refactoring
of the dashboard data flow to properly type. TypeScript compilation passes.

src/app/dashboard/clients/page.tsx

@@ -4,7 +4,6 @@ import { PageHeader } from "~/components/layout/page-header";
 import { Button } from "~/components/ui/button";
 import { HydrateClient } from "~/trpc/server";
 import { ClientsTable } from "./_components/clients-table";
-import { Card, CardContent } from "~/components/ui/card";
 
 export default async function ClientsPage() {
   return (