Document full-stack setup; fix dev proxy; drop stray temp script

- README rewritten for the completed frontend: full setup/run instructions
  (Docker Compose, local dev with hot reload, prod build), pages/routes,
  API endpoints, and a consolidated environment-variable reference
- Vite dev proxy now targets 127.0.0.1 (avoids the Windows IPv6-localhost
  pitfall where the SPA could not reach the IPv4-bound API)
- Remove server/_setup.ps1 (a scratch script accidentally committed in the
  previous frontend commit) and gitignore _*.ps1 scratch files

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

client/vite.config.js

@@ -9,8 +9,8 @@ export default defineConfig({
   server: {
     port: 5173,
     proxy: {
-      '/api': { target: 'http://localhost:3000', changeOrigin: true },
-      '/uploads': { target: 'http://localhost:3000', changeOrigin: true },
+      '/api': { target: 'http://127.0.0.1:3000', changeOrigin: true },
+      '/uploads': { target: 'http://127.0.0.1:3000', changeOrigin: true },
     },
   },
   build: {