feat: complete tRPC integration and fix platform UI issues

- Implement comprehensive tRPC setup with type-safe API
- Create tRPC routers for dashboard, admin, and auth endpoints
- Migrate frontend components to use tRPC client
- Fix platform dashboard Settings button functionality
- Add platform settings page with profile and security management
- Create OpenAI API mocking infrastructure for cost-safe testing
- Update tests to work with new tRPC architecture
- Sync database schema to fix AIBatchRequest table errors

server/routers/_app.ts

@@ -0,0 +1,23 @@
+/**
+ * Main tRPC Application Router
+ *
+ * This file combines all individual routers into a single app router.
+ * All tRPC endpoints are organized and exported from here.
+ */
+
+import { router } from "@/lib/trpc";
+import { authRouter } from "./auth";
+import { dashboardRouter } from "./dashboard";
+import { adminRouter } from "./admin";
+
+/**
+ * Main application router that combines all feature routers
+ */
+export const appRouter = router({
+  auth: authRouter,
+  dashboard: dashboardRouter,
+  admin: adminRouter,
+});
+
+// Export type definition for use in client
+export type AppRouter = typeof appRouter;