feat(web): management console frontend

Vue 3 + TS + Vite + Tailwind with self-built UI components. Landing,
auth, user dashboard (keys/usage/settings), and admin console
(overview/models/channels/users/usage/config). Theme system
(light/dark/system) with pre-paint boot script, theme-aware ECharts,
and a channel editor with multi-format (Anthropic/OpenAI) selection.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

web/vite.config.ts

@@ -0,0 +1,31 @@
+import { defineConfig } from 'vite'
+import vue from '@vitejs/plugin-vue'
+import { fileURLToPath, URL } from 'node:url'
+
+// Dev: proxy /api and /v1 to the Go backend so the browser stays same-origin
+// (no CORS, and the HttpOnly refresh cookie flows through the proxy).
+const backend = process.env.VITE_PROXY_TARGET || 'http://localhost:18080'
+
+export default defineConfig({
+  plugins: [vue()],
+  resolve: {
+    alias: {
+      '@': fileURLToPath(new URL('./src', import.meta.url)),
+    },
+  },
+  server: {
+    port: 5173,
+    proxy: {
+      '/api': { target: backend, changeOrigin: true },
+      '/v1': { target: backend, changeOrigin: true },
+    },
+  },
+  preview: {
+    host: true, // bind 0.0.0.0 so the built SPA is reachable over the public IP
+    port: 5173,
+    proxy: {
+      '/api': { target: backend, changeOrigin: true },
+      '/v1': { target: backend, changeOrigin: true },
+    },
+  },
+})