fix Discord timestamp calculation

Incorrect output:

```
Created commit [update `/example` shortlink](https://acmcsuf.com/code/commit/0333b548246fbddd8c309637f06fd31b14d6f805)!

This shortlink will be expire in <t:1696195785765:R>.
```

main.ts

@@ -135,9 +135,11 @@ export function makeHandler(kv: Deno.Kv) {
             if (ttlDuration) {
               // Render to Discord timestamp format.
               // https://gist.github.com/LeviSnoot/d9147767abeef2f770e9ddcd91eb85aa
-              const discordTimestamp = `<t:${Date.now() + ttlDuration.raw}:R>`;
+              const discordTimestamp = toDiscordTimestamp(
+                (Date.now() + ttlDuration.raw) * 0.001,
+              );
               content +=
-                `\n\nThis shortlink will be expire in ${discordTimestamp}.`;
+                `\n\nThis shortlink will be expire ${discordTimestamp}.`;
             }
 
             // Send the success message.
@@ -229,3 +231,7 @@ export function makeShorterOptions(
     },
   };
 }
+
+function toDiscordTimestamp(timestamp: number) {
+  return `<t:${timestamp}:R>`;
+}