fix: dev proxy za frontend API pozive

U dev modu frontend sada koristi /api preko Astro/Vite proxy sloja prema backend servisu, umjesto direktnog gađanja localhost:8001 iz browsera.\n\nTime se uklanja ERR_CONNECTION_REFUSED u lokalnom Docker development okruženju.\n\nCo-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

frontend/astro.config.mjs

@@ -19,6 +19,7 @@ const allowedHosts = Array.from(
 const hmrHost = process.env.PUBLIC_HMR_HOST || 'localhost';
 const hmrProtocol = process.env.PUBLIC_HMR_PROTOCOL || 'ws';
 const hmrClientPort = Number(process.env.PUBLIC_HMR_CLIENT_PORT || 4321);
+const apiProxyTarget = process.env.PUBLIC_API_PROXY_TARGET || 'http://localhost:8001';
 
 export default defineConfig({
   output: 'server',
@@ -59,6 +60,12 @@ export default defineConfig({
             host: hmrHost,
             clientPort: hmrClientPort,
           },
+          proxy: {
+            '/api': {
+              target: apiProxyTarget,
+              changeOrigin: true,
+            },
+          },
           watch: {
             usePolling: true,
             interval: 100,