refactor(api): version routes and externalize client base url

- serve REST endpoints under /api/v1 with root exceptions for health and mcp

- move swagger UI to /docs and allow direct frontend calls via CORS

- remove Vite proxy/hash routing and rely on env-driven VITE_API_URL

client/src/api/client.ts

@@ -13,9 +13,9 @@ import type {
 } from './types';
 import { emitApiErrorToast } from '../lib/toast-events';
 
-// In dev, Vite proxies /environments /sessions /scenarios to localhost:3000.
-// In production (or when VITE_API_URL is set) we hit the configured origin directly.
-const BASE_URL: string = (import.meta.env.VITE_API_URL as string | undefined) ?? '';
+// API calls are versioned under /api/v1 by default.
+// Set VITE_API_URL (for example, http://localhost:13000/api/v1) to use a different origin.
+const BASE_URL = ((import.meta.env.VITE_API_URL as string | undefined) ?? '/api/v1').replace(/\/$/, '');
 
 async function request<T>(path: string, init?: RequestInit): Promise<T> {
   let res: Response;