Standardize SurClaw ports away from defaults

- Change the API default listen port from 3000 to 3100 and include the Docker frontend origin in default CORS.

- Point Vite's default API proxy, Docker API container port, and Nginx upstream to 3100.

- Keep Docker host ports on 4002 for web, 3002 for API, and 5433 for PostgreSQL.

- Update environment examples and documentation to remove stale localhost:3000 guidance.

vite.config.ts

@@ -6,7 +6,7 @@ import {defineConfig} from 'vitest/config';
 
 export default defineConfig(({mode}) => {
   const env = loadEnv(mode, '.', '');
-  const apiProxyTarget = env.VITE_API_PROXY_TARGET || 'http://localhost:3000';
+  const apiProxyTarget = env.VITE_API_PROXY_TARGET || 'http://localhost:3100';
   return {
     plugins: [react(), tailwindcss()],
     resolve: {