fix(frontend): anchor Vite dev proxy so /login.html isn't forwarded

The /login proxy entry was matching any path starting with /login —
including /login.html, which Vite is supposed to serve itself. Without
the Go backend running, this caused ECONNREFUSED noise on every page
load.

Switched to regex patterns anchored with ^...$ so only the bare backend
paths (/login, /logout, /getTwoFactorEnable) and explicit sub-routes
(/panel/*, /server/*) get proxied. Static .html files Vite serves
directly are no longer matched.

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

frontend/vite.config.js

@@ -32,10 +32,11 @@ export default defineConfig({
     strictPort: true,
     proxy: {
       // Proxy API calls during `npm run dev` to the local Go panel.
-      '/panel': 'http://localhost:2053',
-      '/server': 'http://localhost:2053',
-      '/login': 'http://localhost:2053',
-      '/logout': 'http://localhost:2053',
+      // Patterns are anchored regex so /login.html and /index.html
+      // (which Vite serves itself) are NOT forwarded — only the bare
+      // backend paths and their sub-routes.
+      '^/(login|logout|getTwoFactorEnable)$': 'http://localhost:2053',
+      '^/(panel|server)(/|$)': 'http://localhost:2053',
     },
   },
 });