Milestone 3: catalog sync, batch transactions, and reports

- GET /api/v1/catalog/sync?since= — delta sync for Android offline-first
- POST /api/v1/transactions/batch — idempotency-keyed batch upload (207 Multi-Status),
  validates product ownership, skips duplicates silently
- GET /api/v1/transactions + /reports/summary — paginated list and aggregated
  revenue/tax/top-product reporting with date range filters
- ReportsPage: stat cards, payment method breakdown, top-10 products, transaction table
- Reports added to sidebar nav and router

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

server/src/app.ts

@@ -9,6 +9,8 @@ import usersRouter from "./routes/users.js";
 import categoriesRouter from "./routes/categories.js";
 import taxesRouter from "./routes/taxes.js";
 import productsRouter from "./routes/products.js";
+import catalogRouter from "./routes/catalog.js";
+import transactionsRouter from "./routes/transactions.js";
 import { errorHandler } from "./middleware/errorHandler.js";
 
 const __filename = fileURLToPath(import.meta.url);
@@ -34,6 +36,8 @@ export function createApp() {
   app.use("/api/v1/categories", categoriesRouter);
   app.use("/api/v1/taxes", taxesRouter);
   app.use("/api/v1/products", productsRouter);
+  app.use("/api/v1/catalog", catalogRouter);
+  app.use("/api/v1/transactions", transactionsRouter);
 
   // Serve React admin UI static assets in production
   if (process.env.NODE_ENV === "production") {