feat: implement complete invoicing application with CSV import and PDF export

- Add comprehensive CSV import system with drag-and-drop upload and validation
- Create UniversalTable component with advanced filtering, searching, and batch actions
- Implement invoice management (view, edit, delete) with professional PDF export
- Add client management with full CRUD operations
- Set up authentication with NextAuth.js and email/password login
- Configure database schema with users, clients, invoices, and invoice_items tables
- Build responsive UI with shadcn/ui components and emerald branding
- Add type-safe API layer with tRPC and Zod validation
- Include proper error handling and user feedback with toast notifications
- Set up development environment with Bun, TypeScript, and Tailwind CSS

src/server/api/root.ts

@@ -0,0 +1,25 @@
+import { clientsRouter } from "~/server/api/routers/clients";
+import { invoicesRouter } from "~/server/api/routers/invoices";
+import { createCallerFactory, createTRPCRouter } from "~/server/api/trpc";
+
+/**
+ * This is the primary router for your server.
+ *
+ * All routers added in /api/routers should be manually added here.
+ */
+export const appRouter = createTRPCRouter({
+  clients: clientsRouter,
+  invoices: invoicesRouter,
+});
+
+// export type definition of API
+export type AppRouter = typeof appRouter;
+
+/**
+ * Create a server-side caller for the tRPC API.
+ * @example
+ * const trpc = createCaller(createContext);
+ * const res = await trpc.clients.getAll();
+ *       ^? Client[]
+ */
+export const createCaller = createCallerFactory(appRouter);