feat(server): add graceful shutdown handling

- Introduce signal listeners for SIGINT and SIGTERM to handle shutdown
- Use AbortController to terminate the server gracefully
- Improve server reliability and resource cleanup during termination

src/main.ts

@@ -3,6 +3,7 @@ import { Env } from './env.ts';
 import { ltProxyAuth } from './ltProxyAuth.ts';
 import { ltProxyHandler } from './ltProxyHandler.ts';
 
+const ac = new AbortController();
 const httpKernel = new HttpKernel();
 
 httpKernel.route({
@@ -11,9 +12,19 @@ httpKernel.route({
 }).middleware(ltProxyAuth).handle(ltProxyHandler);
 
 Deno.serve({
+    signal: ac.signal,
     port: Env.proxyPort,
     hostname: Env.proxyHost,
     onListen: ({ hostname, port }) => {
         console.info(`lt-auth-proxy listening on ${hostname}:${port}`);
     },
 }, async (req) => await httpKernel.handle(req));
+
+const shutdown = () => {
+    console.info('Shutting down the server...');
+    ac.abort();
+    console.info('Server shut down successfully.');
+};
+
+Deno.addSignalListener('SIGINT', shutdown);
+Deno.addSignalListener('SIGTERM', shutdown);