fix: use npm install in Dockerfile, add static file serving

- Dockerfile uses npm install (no lockfile yet, kaniko builds in-cluster)
- Server serves client build from ./public in production
- SPA fallback for client-side routing

server/src/index.ts

@@ -1,5 +1,7 @@
 import express from 'express';
 import cors from 'cors';
+import path from 'path';
+import { fileURLToPath } from 'url';
 import { createServer } from 'http';
 import { config } from './config.js';
 import { closeDb } from './db/index.js';
@@ -10,6 +12,8 @@ import authRoutes from './routes/auth.js';
 import connectionsRoutes from './routes/connections.js';
 import messagesRoutes from './routes/messages.js';
 
+const __dirname = path.dirname(fileURLToPath(import.meta.url));
+
 const app = express();
 
 app.use(cors({ origin: config.CORS_ORIGIN, credentials: true }));
@@ -23,6 +27,16 @@ app.use('/api/auth', authRoutes);
 app.use('/api/connections', connectionsRoutes);
 app.use('/api/messages', messagesRoutes);
 
+// Serve static frontend in production
+const publicPath = path.resolve(__dirname, '../public');
+app.use(express.static(publicPath));
+app.get('*', (_req, res, next) => {
+  if (_req.path.startsWith('/api') || _req.path.startsWith('/ws')) {
+    return next();
+  }
+  res.sendFile(path.join(publicPath, 'index.html'));
+});
+
 const server = createServer(app);
 
 createWebSocketServer(server);