Add managed catalog sync and player UX improvements

vite.config.js

@@ -1,11 +1,77 @@
 import { defineConfig } from 'vite';
 import react from '@vitejs/plugin-react';
 import { resolve } from 'node:path';
+import { readFile, stat } from 'node:fs/promises';
+
+const MANAGED_CATALOG_API_PATH = '/api/managed-stations.json';
+
+async function loadManagedCatalogEnvelope(repoRoot) {
+  const candidates = [
+    resolve(repoRoot, 'public', 'stations.json'),
+    resolve(repoRoot, 'dist', 'stations.json'),
+    resolve(repoRoot, 'stations.json'),
+  ];
+  let found = null;
+  for (const p of candidates) {
+    try {
+      const s = await stat(p);
+      if (s.isFile()) { found = { filePath: p, mtime: s.mtime }; break; }
+    } catch { /* try next */ }
+  }
+  if (!found) throw new Error('Managed catalog source file was not found.');
+  const raw = JSON.parse(await readFile(found.filePath, 'utf8'));
+  const stations = Array.isArray(raw) ? raw : raw.stations;
+  return { schemaVersion: 1, updatedAt: found.mtime.toISOString(), stations };
+}
 
 const buildStamp = `${Date.now()}`;
 
+function managedCatalogApiPlugin() {
+  async function handleManagedCatalogRequest(req, res, next) {
+    if (!req.url) {
+      next();
+      return;
+    }
+
+    const requestUrl = new URL(req.url, 'http://127.0.0.1');
+    if (requestUrl.pathname !== MANAGED_CATALOG_API_PATH) {
+      next();
+      return;
+    }
+
+    try {
+      const payload = await loadManagedCatalogEnvelope(process.cwd());
+      res.statusCode = 200;
+      res.setHeader('content-type', 'application/json; charset=utf-8');
+      res.setHeader('cache-control', 'no-store');
+      res.end(`${JSON.stringify(payload)}\n`);
+    } catch (error) {
+      res.statusCode = 500;
+      res.setHeader('content-type', 'application/json; charset=utf-8');
+      res.end(JSON.stringify({
+        error: 'Failed to load managed catalog',
+        message: error instanceof Error ? error.message : 'Unknown error',
+      }));
+    }
+  }
+
+  return {
+    name: 'managed-catalog-api',
+    configureServer(server) {
+      server.middlewares.use((req, res, next) => {
+        void handleManagedCatalogRequest(req, res, next);
+      });
+    },
+    configurePreviewServer(server) {
+      server.middlewares.use((req, res, next) => {
+        void handleManagedCatalogRequest(req, res, next);
+      });
+    },
+  };
+}
+
 export default defineConfig({
-  plugins: [react()],
+  plugins: [react(), managedCatalogApiPlugin()],
   base: './',
   build: {
     rollupOptions: {