Initial scaffold: full-stack RackMapper application

Complete project scaffold with working auth, REST API, Prisma/SQLite
schema, Docker config, and React frontend for both Rack Planner and
Service Mapper modules. Both server and client pass TypeScript strict
mode with zero errors. Initial migration applied.

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

server/middleware/errorHandler.ts

@@ -0,0 +1,22 @@
+import { Request, Response, NextFunction } from 'express';
+import { AppError, err } from '../types/index';
+
+export function errorHandler(
+  error: Error,
+  _req: Request,
+  res: Response,
+  _next: NextFunction
+): void {
+  const statusCode = error instanceof AppError ? error.statusCode : 500;
+  const code = error instanceof AppError ? error.code : 'INTERNAL_ERROR';
+  const message =
+    process.env.NODE_ENV === 'production' && statusCode === 500
+      ? 'Internal server error'
+      : error.message;
+
+  if (statusCode === 500 && process.env.NODE_ENV !== 'production') {
+    console.error('[ErrorHandler]', error);
+  }
+
+  res.status(statusCode).json(err(message, code ? { code } : undefined));
+}